Vague storyline that bears little in common with the actual storyline... :-)
Somebody is mauled. So they lock up Oz (the happens to be a werewolf). Xander comes to do night watch with some reading material.
And has a discussion with Willow.
Xander falls asleep. Stuff happens. Another guy turns up slightly mauled and nibbled on. As the window was open, they kinda had reason to suspect Oz.
Oz, upset, wants to do the manly thing and leave. But, it's that time. So he locks himself in the cage and tells Willow he's going to turn wolfy. Go away...
(imagine that, a shy werewolf!)
Willow, determined to clear Oz, breaks into the morgue (like you do) and examines the body with medical precision, much to the disgust of Xander and Cordelia.
As soon as she's finished, she faints. Too much gore for lil'Willow.
To cut a long and Willow-free part short, it wasn't Oz. It was some creepy monster-boy who beat up (and then killed) his girlfriend. (Willow's comment "I think we broke her" as the girlfriend freaks out was classic!) Well, Buffy accidently darts Giles with the stun gun. Faith follows and darts Oz (wolf), Buffy follows and beats up monster-boy and someplace in the middle of it all, Angel crashes in and saves her. Um, yeah. Something like that.
All that excitement is followed by another day at High School. Only in America!