Revealing mistake: The Prowler's just killed Lisa in the pool, yet he's walking across a lawn completely dry. Clearly this is footage reused from when he was outside the dorm earlier.
Continuity mistake: At the end of the movie when Pam returns to her dorm room she heads to the bathroom for the final surprise. When she walks towards the bathroom door you can see the door is only slightly ajar, however when the shot changes to inside the bathroom the door is now almost fully open (open enough to see Pam fully).
Plot hole: After the first murder in Pam's dorm room there should be blood everywhere but when Pam returns to change her dress there is only a single stripe of it on the bedsheets.
