A native of Roanoke, Virginia, Donnelly studied Law at Northwestern University. In August 1998 he joined the FBI after graduating from Quantico with honors. He began with the Miami, FL field office in Counter Terrorism until he distinguished himself as an investigator and became a highly sought-after agent. In subsequent years, he moved from Miami to Portland in 2000, then to San Diego in 2003. He was promoted to supervisory special agent for the Boston Field Office in 2007 and worked there until 2011. He was then transferred to New York City. (“Prisoner's Dilemma”)
He first appears investigating Scott Powell for the murder of Congressman Michael Delancey. He first encounters The Man in the Suit when he breaks out Scott Powell from the FBI's custody. Powell was later proven innocent when Finch uses a forced pairing of Pete Matheson's cell phone to record an incriminating call between him and Root, but Donnelly started suspecting Reese of being a mercenary. (“Root Cause”)
He informs Carter that the FBI has information about DNA that ties Reese to a case involving smugglers (“Blue Code”) and a cold case from 2011 in New Rochelle, New York. He invites Carter to assist on the investigation and she accepts. In New Rochelle, he discovers the fact that Peter was in debt to loan sharks and he hypothesizes that the loan sharks had hired Reese to kill him. (“Many Happy Returns”)
Using the NYPD's Real Time Crime Center, Donnelly and his FBI agents hunt Reese and Caroline Turing through a hotel, not knowing that Carter is alerting Reese to their movements while a mole lets HR know as well. Donnelly's men nearly corner Reese and Turing, but Harold Finch is able to disable their access to the cell phone network, preventing Donnelly and Simmons orders from getting to their respective men in time for Reese and Turing to escape. Donnelly later receives an anonymous email from Fusco with pictures of the HR Inner Council and Detective Sagan, the mole who aided Simmons and his men. Donnelly then uses the information to arrest Sagan. (“Firewall”)
Weeks later, Donnelly leads a massive FBI crackdown on HR, arresting over 75 dirty cops on information covertly gathered and supplied by Fusco. Donnelly tells Carter that he still intends to chase "the Man in the Suit" once he's wrapped things up with HR, but they haven't captured HR's leader, who he doesn't believe to be a cop. Donnelly tells Carter that he's following up on a lead regarding that and will keep her in the loop. Carter later calls Reese and tells him that she got a call from Donnelly that Maxine Angelis' story about Christopher Zambrano being the head of HR is not true, with the FBI not even considering him a suspect.
After Zambrano is murdered, Donnelly arrives at the police station to question Maxine, unknowingly encountering Reese in the process. Maxine shows him the call she got with the anonymous tip about Zambrano and Donnelly tells her she screwed up badly as Zambrano wasn't the head of HR, he was a witness who could bring the boss down. Donnelly explains that Zambrano, who was an honest man unlike his Mafia Don father, found a ledger his father had on HR and was going to turn it over to the FBI in exchange for an immunity deal which had come in that night. Donnelly finds out that the number that called Maxine was from a disposable cell phone and warns her that she may have ruined the FBI's only chance to catch the head of HR. After Maxine exposes Landon Walker as the apparent head of HR, Donnelly arrests him for receiving bribes, enterprise corruption and conspiracy. However, unknown to Donnelly, the real head of HR is able to escape detection. (“Bury the Lede”)
Donnelly visits Carter at the police station, interrupting her talk with Detective Cal Beecher about the disappearance of Ian Davidson. Donnelly tells Carter that the FBI is switching their focus back to "the Man in a Suit" now that HR has been degraded to the point of irrelevance and that he wants her help but needs her to take a temporary position in the FBI to do it. Donnelly leaves Carter to think it over, but tells Carter that with her skills, her temporary job could become permanent. He later asks Carter again for help but needs an answer before he can tell her anything. Carter finally agrees and Donnelly tells Carter that after analysis of the cell phone towers from the night that they lost Reese, the analysts at Quantico found a cloned IMEI with a unique signature which Donnelly realized belonged to Reese. Donnelly tells Carter that he had the FBI computers search for that signature which popped up at a recent robbery. With the signature, Donnelly can track Reese the next time he uses his phone. The next day, Donnelly gets word that the signature has been detected at an investment bank where a 911 call of an explosion originated. Carter secretly warns Finch through Fusco and Donnelly and his SWAT team clear the bank. Donnelly is pleased when it seems they've captured "the Man in a Suit", but discovers that they caught four men in suits. After Carter claims to be unable to recognize the correct one, Donnelly has all four men taken into custody. (“Shadow Box”)
After the arrest of the four men, Donnelly takes the to Rikers Island where he has their DNA taken and orders the four men put into lockdown. Donnelly tells Warden Hutchins that one of the four is the most dangerous man he has ever chased and he has 72 hours to hold them without charges. The warden reluctantly agrees to give him that long and Donnelly tells Carter that he doesn't need to interrogate the men as he has "the Man in the Suit's" DNA from New Rochelle, his blood from the burned car and his fingerprints thanks to Carter. Donnelly is sure he has "the Man in the Suit" and is pleased, not noticing how worried Carter is by the news.
Donnelly eventually gets the news that the DNA matches none of the men in their custody and determines that "the Man in the Suit" and the people he works for somehow got to the DNA samples. Donnelly orders the DNA run again at an FBI lab and stops the men from being released, stating that they are now classified as enemy combatants and will stay locked up. Donnelly tells Carter that this is their last chance to identify "the Man in the Suit" as if he escapes now, they will never catch him again. Donnelly explains to Carter that he has been burned by "the Man in the Suit" too many times and can only trust Carter, the person who has been hunting the man from the beginning. Donnelly asks for Carter to put her experience in interrogation in the military to use in interrogating his suspects, starting with Reese. (“2πR”)
Donnelly watches as Carter interrogates the four suspects and checks out each of the identities they give. When the warden brings concerns about Donnelly's methods, Donnelly uses the warden's own violations to keep him off of his back. Donnelly tells Carter that all of the prisoners stories check out, but the people he suspects "the Man in a Suit" to work for could create an airtight alibi. As his men check out the out-of-state addresses of the three other suspects, Donnelly takes Carter to check out John Warren who works on Wall Street. Donnelly finds the office of an apparently ordinary man due to Finch having carefully created the cover, but has his people take the firm's hard drives and check IDs to be sure. He then approaches Carter and tells her that while the whole thing looks real, it could be a sign of how long "the Man in the Suit" has been undercover. Donnelly then gives Carter a wireless earpiece so they can communicate during interrogations and better work together.
Donnelly watches as Carter interrogates Warren again and orders her to press Warren more. After Warren is uncomfortable about killing a Serbian militant, Donnelly orders Carter to press Warren on the topic since it is clearly a touchy subject for Warren. As Warren gives his story, Donnelly checks into and finds records confirming each part of the story. After Warren recognizes Carter as a former military interrogator, Donnelly pulls her out, demanding to know why she wasn't listening to him. Carter tells Donnelly that she was trying to earn his trust and Donnelly admits that Warren's story checks out and moves onto interrogating the other suspects. After Carter's continued pushing breaks the story of one, Donnelly comes in, having identified the man as Brian Kelly, an ex-Navy SEAL. However, Donnelly tells her they can eliminate Kelly as a suspect due to him being in Iraq at the time of "the Man in the Suit's" actions in New Rochelle. The two are then interrupted by the warden for the prisoners daily food and exercise.
After the prisoners return, Carter resumes her interrogation of Warren as Donnelly observes and gives directions. As Warren's story continues to check out, Donnelly interrupts Carter's interrogation to tell her that one of the other prisoners is ready to talk. The prisoner identifies himself as Charles Macavoy and offers anything they want to know in exchange for an immunity deal. Donnelly bursts in and demands to know if Macavoy committed any of the crimes "the Man in a Suit" is known for and can tell by his reaction that he didn't. Donnelly promises Macavoy his deal if he will give them "the Man in a Suit" and Macavoy agrees. However, Finch sets the fire alarm off before Macavoy can tell them anything and everyone is evacuated. When Macavoy returns, he identifies the third suspect as "the Man in a Suit", satisfying Donnelly until he gets word that Kelly apparently hung himself in his cell. Donnelly realizes that someone got to both Kelly and Macavoy and as someone has been sabotaging the investigation from the start and Macavoy is nervous, becomes convinced that Warren is the man they are looking for.
Donnelly has Carter interrogate Warren again, asking her to find someone he loved. On Finch's orders to stall so he can create a fake girlfriend, Carter briefly shares the story of the first time she killed a man before asking Warren if he ever loved anyone. Warren tells Carter about Allison West, the woman he loved and chose not to go back to the military after 9/11 for. Donnelly finds that Allison West checks out and decides to perform one last test of Warren: having noticed Byron and his gang hassling Warren earlier, Donnelly puts Warren into the courtyard and removes the guards, trying to force Warren to show his fighting skills. Warren is beaten by the Aryan gang members before Elias steps in and ends the fight. Donnelly is left with a thoroughly-disgusted Carter who tells Donnelly he used to be a good man but ever since the investigation started, he has been bending the rules and went over the line by trapping Warren as he did. As Donnelly tries to defend his actions, Carter tells him all he has to do is watch and interrogates Wayne Packer, the last suspect. Carter is able to get Packer to admit his name and that he has a boss and when Carter demands the name of Packer's boss or if she should just arrest him as "the Man in a Suit", Packer strangles her. After Packer is pulled off of Carter and placed in handcuffs, she tells Donnelly that he has his "Man in a Suit." With no other choice, Donnelly is forced to release Warren as Packer has been implicated as "the Man in a Suit."
As Carter and Reese reunite on a bridge and discuss their victory, they are approached by Donnelly at gunpoint who now knows that Reese is "the Man in a Suit." Donnelly congratulates Carter on catching Reese and allows Carter to handcuff him before doing the same to her himself. Donnelly is disgusted that Carter threw away a promising career to help Reese and as he drives them to a safe house, explains that he knew he had a mole after Reese escaped him the first time and started to think it might be Carter after Reese's fingerprints went missing and the DNA samples got switched. Donnelly tells them that he knew Carter was working for Reese when he saw the genuine concern in her eyes for him when he made Reese face the Aryan gang and asks what price Reese paid Carter to make her help him. Carter admits that she wasn't paid anything and is just helping a friend. Donnelly insists that Carter has been tricked into becoming an asset for a private intelligence firm and doesn't believe that they are actually helping people stating that Reese is nothing more than a highly-trained murderer and chose that life and to become the monster Donnelly believes Reese is.
As he continues to the safe house, Donnelly gets a call from Finch who had received Donnelly's number from the Machine. Finch warns Donnelly to stop, that he has a source that states the agent is in great danger, but Donnelly's SUV is hit from the side by a dump truck and crashes. As Donnelly looks on helplessly, Kara Stanton approaches and shoots Donnelly twice with a silenced pistol, killing him before abducting Reese. (“Prisoner's Dilemma”)
Following Donnelly's death, Carter wakes up and informs Finch who calls her that Donnelly is dead. Carter is able to retrieve Donnelly's handcuff keys and free herself and reluctantly flees the scene of Donnelly's death on Finch's orders. The next morning, Carter is called to the scene by Fusco where SAIC Brian Moss questions Carter on Donnelly's activities. Moss tells Carter that because of Donnelly's obsession with "the Man in a Suit" case and his belief that "the Man in a Suit" had backing from the government, the FBI had begun to think that Donnelly had become paranoid and lost his perspective. When asked what Carter thinks, Carter tells Moss that she thinks Donnelly was a good agent rather than reporting on his increasingly erratic behavior to catch Reese.
A few days after Donnelly's death and the deaths of Mark Snow and Kara Stanton, Carter is visited by Moss who tells her that they identified Snow and Stanton as the two suicide bombers who broke into a DOD facility. As Snow matches the description of "the Man in a Suit", the FBI now believes that Donnelly got too close to the truth and Snow and Stanton murdered him to cover it up. With Snow dead, the FBI officially closes the investigation into "the Man in a Suit." (“Dead Reckoning”)
Not long after Donnelly's death, Carter is visited by SAIC Brian Moss who had begun going over some of Donnelly's old files after his death. Moss finds a recommendation from Donnelly for Carter to join the FBI as a field agent and offers to honor Donnelly's recommendation and begin the process. While Carter agrees, she is ultimately disqualified due to her connection to Cal Beecher. (“Booked Solid”)
After Reese catches Carter running surveillance on HR, he tells her that Finch has determined that Carter has gathered evidence on half of HR and can use it to force the dirty cops she has evidence against to make deals to turn in the other half. However, Carter tells Reese that that was Donnelly's mistake: he didn't identify HR's boss which allowed HR to rebuild itself out of the ashes. Carter also suggests that if Donnelly had been able to take down HR's boss, Cal Beecher would've survived. Carter tells Reese she is determined not to make the same mistake Donnelly did and not make a move until she has identified HR's boss. (“Razgovor”)
- “Bury the Lede”
- “Shadow Box”
- “Prisoner's Dilemma”
- “Dead Reckoning” (“Prisoner's Dilemma” footage and corpse only)