In the season 4 episode "Mr. Monk and the Captain's Marriage," when Leland is working on the murder of Jimmy "Chicklet" Botsdale, one of the cops on the scene, Sergeant Ryan Sharkey Jr. claims to be having an affair with Karen. Leland punches him and afterwards, he decides to ask Karen if she knows Sharkey. Karen suspiciously denies it, but Leland suspect that it might prove why she's taken to sleeping in the guest room (which she claims is because of his snoring) and her forgetting their anniversary.