Starsky knocks the bowl out of Hutch's hand, spilling popcorn all over the table. The next shot shows most of the popcorn over by Hutch.
It could debated whether the production ran out of time to clarify every plot hole in a way that made sense, or if the viewers are left to believe the show meant to say René was a real vampire. The latter seems highly unlikely as this isn't fantasy nor sci-fi genre. Perhaps the editor cut out filmed scenes that explained it all, due to time constraints.
René kills women by biting them and draining them of their blood. Yet neither of the bodies show a bloody neck, nor neck poke marks, even though the coroner confirmed that they are drained of their blood from neck punctures. Equally, there is no blood on René's lips when he runs away after killing them.
When Starsky & Hutch walk into Slade's Cave, the same exact music is playing as the one that did at the club where the boys where hanging out, and which they left at least an hour prior, to go check out the body at the morgue.
It is never explained how exactly René intended to use the deaths to revive his dead wife.
It is never explained whether René was really crippled and had a split personality allowing him to run in his vampire alter ego, (as would appear if one is to believe he is sincere when he tells Starsky & Hutch he knew nothing of his students' deaths) or if was faking being crippled. The later is unlikely, since he told the detectives he was injured in '61 and there were records to prove it.
Hutch phones in to get intel on René, yet none is given to explain why he kills or whether he is really crippled or a fake.