After being separated for 38 years by the Korean War, Jean Pargetter and Lionel Hardcastle suddenly meet again after he seeks help from her secretarial agency.
After Lionel checks out of the hotel without telling Jean, she figures they will not be renewing their relationship. However, after Lionel's publisher, Alistair, asks him to go to a party to meet with some people about his book, he asks Jean to attend with him.
Since Lionel is about to go on a lecture tour, he asks Jean to spend the day with him. The two decide to visit some of their old haunts, only to find that a lot has changed since they were last together.
Judith convinces Jean to surprise Lionel on his lecture tour by visiting him in Norwich. However, it's Jean who gets the bigger surprise when she discovers Lionel is with another woman.
As Lionel is trying to smooth things over with Jean over what happened in Norwich, Jean is being pursued by Alistair, who refuses to take no for an answer.
After finding out that Judith is now in love with Lionel and Alistair is still pursuing her, Jean decides that she, Lionel, Judith and Alistair all go on a picnic. The idea is that this will make Judith and Alistair fall for one another, but it ends up making Jean and Lionel grow closer together.
Jean is concerned about Alistair's relationship with both Judith and Sandy. When questioned about it by Lionel, Alistair explains that they are just mates, nothing else. Meanwhile Lionel receives mail from his ex-wife, Margaret, and he and Jean go down to the hotel to visit her. Margaret introduces them to her current companion, a much younger Gary. In separate conversations with Lionel and Jean, both Judith and Sandy tell them that they are each trying to push Alistair towards the other.
Lionel is dumbfounded by the delivery of two cots to the Hardcastle residence, given that there are no babies in the house. So Jean explains they're for their grandchildren, which is even more surprising given that Judith isn't even pregnant. However, it turns out it's not for want of trying, but as their daughter soon reveals, husband Alistair may have a medical condition that prevents them from ever having kids
To make matters worse, family friend Sandy is back from Canada with other half Harry, who has decided to apply for a job in the police armed response unit - a decision which is threatening to drive a wedge between the happy couple.
The visitor's unexpected arrival puts the cat among the pigeons for Lionel, and when the truth finally comes out, Jean takes great delight in introducing him to the rest of their family and friends.