Later, a janitor loses a quarter under the stairs and locates a crate marked Arctic Exhibition June 19, 1834, which he drags out with the help of Dexter because I guess that quarter was worth dying for. They decide to open the thing with a crowbar in a random lab and it turns out to be a kind of fuzzy baboon type creature and it's hungry af. So it chows down on the janitor while a cowardly Dexter runs like a thief in the night.
Again failing to notify the police, Dex instead runs to Henry's house, where Henry has pathetically arranged his chess set for just such a situation. Wilma is out, at some casino or bar or specialized bitch classes, or whatever the movie wants us to think. Dexter tells Henry his crazy ass ape stories, and, being a good friend, Henry's first thought is to drug Dexter and write a long letter to lure Wilma down to the school to be eaten. The story he concocts is that Dexter raped a young female student and she's now cowering beneath the stairs and won't come out. Apparently this story is not difficult to believe, but, sure, Wilma is the real enemy here, why not? While Wilma is on her way, Henry cleans up the lab spic and span from the other two kills. The killer baboon thing, it seems, has pushed its own crate back under the stairs and just wants to go the eff back to sleep after its huge meal, which I can respect. Who among us has not slept for 200 hundred years in a crate beneath some stairs after a trip to Arby's?
As they play their first game of wife-less chess, Dexter is like, wow, I wonder if that prehistoric thing that lasted for hundreds of years without food can survive being drowned in a crate and Henry is all, LOL. The cut scene, ofc, is the murderous baboon breaking out of its crate and being super pissed off, so, anyway, that's how that worked out, glad you can enjoy more free time together, Henry and Dexter.