The Ending Of Only Murders In The Building Season 1 Explained

The proof was right there in Tim Kono's sex toy box: Jan, the sweet bassoonist who inserted herself into the trio, murdered Tim. Early on, Mabel, Charles, and Oliver find a strange item mixed in with his sex toys — when they revisit it in the penultimate episode, they discover it's actually a bassoon cleaner — Jan's bassoon cleaner.

Jan and Tim were dating, but then several things happened: Jan found the emerald ring, assumed Tim was cheating on her, Tim broke up with her, and Jan asked him to come get his things and poisoned his drink. She slipped the fake suicide notes and poisoned glasses into his bag, followed him to his apartment, pulled the fire alarm, and framed his death as a suicide. It should have been obvious when we first met her: Mabel and Charles meet Jan in the elevator, the same place the trio meets and sees Tim, a connection none of the other suspects had. Coincidence?

Why did she do it? Well, Jan is driven by the need to be the most important person in someone's life. It's why she was attracted to both Tim and Charles, loners with few other people to take their attention. It's unclear if Jan's thing about being second started before or after she was passed up for first chair bassoon, but it's clear that plays into it. However, in that moment before a victim's death, Jan relishes being the most important person to them. In an interview with the New York Times, Amy Ryan, who plays Jan, said she believes that Tim was not Jan's first kill.

As for why the writers picked Jan as the killer, co-creator John Hoffman said to A.V. Club that she fit their theme of loneliness and connection the best, but he also hinted that Jan isn't done yet (via Salon.)