S5E1 : The Proposal

We finally found out who Sam's telephone proposal at the end of the last episode was to - Diane! But Diane fears that Sam is meerely on the rebound after breaking up with Janet, so asks him to repeat the proposal in a more romantic occasion, but when he does (on a boat), she refuses, causing Sam to make her walk the plank. Later Diane says she does want to get married, but Sam has now retracted the proposal.