Psych S01 E09 Forget Me Not

"Fake psychic. Real detectives."

Henry's old captain believes he's solved a murder, but his Alzheimer's has caused him to forget the most important details: the crime, and who committed it. Henry calls in Shawn and Gus who find themselves investigating a murder that happened decades ago and only the faulty memory of the retired officer gives them any hope of closing the case.