Jan Bellows is a main character in Only Murders in the Building and the one responsible for the death of Tim Kono. After the death of Tim, Jan began dating Charles-Haden Savage briefly, however this seemed to only be so she could keep tabs on the investigation into Tim's death.
She is later found out to be the murderer and arrested, having killed both Tim and Evelyn, Howard's cat, and attempted to poison Charles.
Relationship with Tim
Little is known about the details of Jan and Tim Kono's relationship, other than they had a complex but irregular relationship. At some point, the relationship became too much for Tim and he tried to call it off. This made Jan angry and as a result, she poisoned Tim and then shot him to cover up the fact that he had been poisoned. Evelyn, Howard's cat, was also killed in the event via poison.
Eventually, Jan would meet Charles-Haden Savage and Mabel Mora in the elevator of the Arconia, and would begin flirting with Charles, which was encouraged by Mabel. The two grew closer and closer and eventually had their first date. Tensions arose between the two when Jan pressed Charles for information on his previous partner, and he called quits on the date earlier than anticipated.
Jan is later approached by Charles again and asked on a second date, to which she agrees. Not long after, the two begin officially dating and Jan joins the investigation into Tim Kono's murder, albeit unofficial. Tensions begin to rise, however, when it is suspected that Jan could be involved in Tim's death, given the bassoon cleaner found in Tim's apartment. Charles pretends that he doesn't suspect her but in reality, he does. Jan realises that Charles suspects she is the murderer and administers the same poison that killed Tim via Charles' handkerchief, thus poisoning him.
In an effort to hide what she has done, Jan heads to the basement of the Arconia where she intends to blow the building up via the gas pipes. Mabel, Oliver, and a severely weakened Charles realise this and are able to head to the basement and stop her before she is able to do any damage. She is arrested shortly after for the murder of Tim Kono.