“Don’t take me for a psycho,” Alexis, the protagonist of François Ozon’s “Summer of ’85,” explains in the film’s opening voice-over. “Corpses are not my thing… Corpses are not my thing. They have a terrible effect on me. Actually, one corpse had a terrible effect on me.” Yet at the conclusion of that pitch-black opening, which is written and framed like a murderer’s confession, Ozon slams into upbeat New Wave music and beautiful bodies on a sunny beach, a single cut that summarizes the style (and, perhaps, the biggest flaw) of the French filmmaker’s latest.