Psych S04 E03 High Noon-ish

"Fake psychic. Real detectives."

Lassiter reluctantly asks Shawn and Gus for help when his surrogate father, sheriff of Sonora, thinks a ghost is wreaking havoc in his town. And even though this Wild West re-creation town is bigger on show than facts, it turns out a real crime is being planned and the murder of the Sheriff's business rival is only the beginning.