The Gruesome Twosome (1967)

Mrs. Pringle and her son Rodney run a wig store which they stock by scalping young coeds who show up to look at the "room for rent." Meanwhile, at the local college, Kathy is determined to figure out who is killing her classmates, much to boyfriend Dave's irritation. When her friend Dawn disappears, Kathy gets closer to the truth as she begins investigating the Pringles' lair.