‘Only Murders in the Building’ Season 3 end: Who was the killer?

The killer of Hollywood superstar Ben Glenroy was finally revealed on Tuesday.

Spoilers ahead for the Season 3 finale of “Only Murders in the Building.” 

The murderer was … Clifford “Cliff” DeMeo (Wesley Taylor), the young Broadway producer of Oliver Putnam’s wacko mystery musical “Death Rattle Dazzle.” 

Well, OK, the crime was mostly committed by Clifford. 

In Episode 10 of the third season of “Only Murders in the Building” — the Hulu series’ cleanest wrap-up so far — viewers learned that the homicide was essentially a two-man job.

The deadly act began with Cliff’s producing partner mother, Donna (Linda Emond).

After reading a leaked, scathing review before the first opening night of “Death Rattle,” which began as a play revival starring Ben Glenroy (Paul Rudd), a famous comic book movie actor, ruthless Donna sprinkled rat poison on a cookie and gave it to Ben. 

But not with the intention of offing him — she only wanted to save her show by sidelining the lousy lead.

“I wasn’t trying to kill Ben, I was just trying to knock him on his ass,” she admits to scrappy podcasters Oliver Putnam (Martin Short), Charles Haden-Savage (Steve Martin) and Mabel Mora (Selena Gomez) after they confront her with their evidence. “To buy us some time.”

Then on the very same night of the poisoning, after Ben’s miraculous recovery, the aptly named Cliff pushed Ben to his actual death down the Arconia’s elevator shaft during a heated spat.

When Ben discovered that Donna had nearly killed him, he told Cliff he was going to call the cops. Furious, the producer’s son shouted that Ben’s “a superhero hack who has no business on Broadway” and angrily shoved the actor, killing him.

After being accused by Oliver, Charles and Mabel, Donna takes the fall for shoving Ben in order to protect Cliff.

But in a dramatic sequence on the second opening night of “Death Rattle Dazzle” — reconceived as a musical — Cliff comes clean as he dangles above the stage of the Gooseberry Theater. 

As always, the third season set up several possible murderers.

There was Gregg (Adrian Martinez), the obsessive fan who posed as Ben’s security guard; Dickie (Jeremy Shamos), Ben’s resentful brother and manager; Loretta (Meryl Streep), Ben’s costar (and, as we learned later, Dickie’s long-lost mother), who called him a “f–king assh–e”); and somxe “Only Murders” fans harbored suspicions about Tobert (Jesse Williams), the ever present documentarian who began dating Mabel.

But in the end, Ben Glenroy was murdered by vicious show business — a Broadway producer who was terrified of a negative review, and the vengeful son who refused to lose his mother.