Walter tries to help his bookkeeper not commit suicide and suffers a mild heart attack at her apartment. At the hospital, he tries to hide the fact he was at a woman's apartment from Maude.
Did You Know?
The infamous "son of a bitch" line is literally the last line of the script. The short exchange between Maude and Walter after that is merely improvised bickering, typical of each episode's closing. See more
[Walter admits that he faked being ill
Oh, Walter, I'm the happiest woman in the world!
[She gets up, hugs him and says through clenched teeth
You son... of... a... bitch!