Warrick Tennyson is the tertiary antagonist from the show monk. He was a career criminal and explosives expert who was hired to build the bomb in 1997 which killed Trudy (Monk's wife).
Dale the Whale tells Monk that Tennyson was involved in the murder in "Mr Monk Goes to Jail" and tells Monk he can find Tennyson in New York. Monk goes to New York in the next episode, "Mr Monk Takes Manhatten", in hope of answers, but finds that Tennyson is dying of heart disease and kidney failure. Because he’s being questioned in connection with a Federal racketeering case, the District Attorney is not letting anyone else see him. The only way for Monk to get access to Tennyson is to solve the recent murder of the Lativan Ambassador.
Having cracked the case, Monk's party is allowed to visit Tennyson on his deathbed. Tennyson remembers being hired by a man to build the bomb that killed Trudy. When asked, he says he doesn’t know the name or the description of the man that hired him, since it was dark when they met, and it looks like Tennyson is a dead end. But Tennyson remembers one vital clue: the man had six fingers on his right hand.
Monk asks for a few moments alone with Tennyson. When the others are gone, Tennyson asks for forgiveness, but Monk cannot bring himself to give it. He turns off Tennyson's morphine drip. But a few tense moments later, he says, "[T]his is Trudy, the woman you killed, turning it back on," and does.
The gang prepare to leave New York, having gotten at least one step further in solving Monk’s most important case.