Two and a Half Men Episode 11.08 Mr. Walden, He Die. I Clean Room.

When Alan learns Lyndsey's boyfriend Larry has hired a P.I. to follow her, suspecting that she has been cheating on him, Alan is at first fearful of being revealed as Lyndsey's mistress. Alan's fears are alleviated when Larry shows him his P.I.'s photo of Walden as the man in question. Apparently, the P.I. took pictures of Lyndsey going into Walden's house. Alan tries talking Larry out of confronting Walden and warns Lyndsey that Larry is coming over. After Larry finds Lyndsey at Walden's house, she explains that she rented the house and hired Jenny to surprise Larry with his fantasy threesome for his birthday. Larry ends up apologizing for ever doubting her fidelity and the three of them, Larry, Lyndsey, and Jenny head upstairs while Alan is left downstairs to listen. Meanwhile, after Walden is spooked by a threatening letter left at his front door, Rose shows up at the house and tells him Larry has been stalking him. Rose offers to take him to a safe place and Walden, grateful for her help, ends up sleeping with her in a seedy motel. We discover Rose was Larry's P.I. and was behind the whole scheme.