The three flatmates plan a party,taking advantage of the fact that the Ropers will be out visiting Mildred's sister and her husband. The evening begins well but turns sour when Liz, whom Robin had previously pursued,takes an interest in Mark,the object of Chrissy's desire - and to cap it all,the Ropers return early.
A group of loud Irishmen are holding sway in the pub, one of whom insults Chrissy. Robin attempts to protest but is made to back down. George, on the other hand, wins the man, Mick's respect for standing up to him over a spilled drink. Robin decides that he will learn self defence and take the man on the next time he sees him. The girls are not sure if this is a good idea.
The flatmates throw a party for the Ropers' wedding anniversary and Robin invites a German student, Franz to come along. Unfortunately this sets off George's obsession with the Second World War,leading to a falling-out between the two men. One of a set of cuff-links bought as a present for George also goes missing and ends up in the food.
To allow Jo to go out on a date Chrissy and Robin agree to baby-sit on her behalf for Mr. and Mrs. Randall but Robin is severely disappointed. The colour television has been sent back, the drinks cabinet is locked with no sign of a key and every time he tries to get close to Chrissy the baby starts crying.
Robin has got the results of his cookery exam and he has failed. He considers moving back to Southampton to work for his father and the two girls are far from pleased at the prospect of his slobbish mate Larry taking over his room. Fortunately Robin's father arrives to talk some sense into him.