Derek Fowler is the floor manager at the Coronet Hotel.
He introduced himself to Finch and Reese when they joined the hotel's staff as a concierge and a bellhop respectively to keep an eye on Mira Dobrica. The two later discovered he was running a prostitution ring out of the hotel.
Throughout the day Fowler harassed Reese to do his job properly and questioned Mira about his side operation, fearing she talked to the police. Mira denied having done so. He later cornered Reese and tried to question him but Reese knocked him out with a single punch.
Fowler was subsequently arrested, and confessed to everything the moment the handcuffs were on.