Jane Waddington, a keen member of the Women's Institute, is discussing interior decoration with her friend George Varley one morning, when she receives a phone call from Beck Enham, the infamous rat-eating junction spotter of Off the Rails. Jane agrees to go junction-spotting with Beck that evening although she dreads the prospect. Beck's daughter Hillary is heard singing in the background.
Jane explains to George that she met Beck on a W.I. trip to Ford in Sussex and foolishly gave her her phone number. She's put Beck off several times before but doesn't want to make her angry.
Don (under an alias as usual) arrives at the door offering to sell some silverware, which he has apparently stolen from HG Transport, but Jane refuses to buy. Don then asks for directions to Combe Road, but Jane has to leave. She meets up with Beck at her home in Leyburn Avenue, South Kensington, where she meets Beck's husband Tom and looks as photos of his school rugby team. He makes a comment that reminds Jane of the Enhams' rat-eating habits, and Jane makes some uneasy enquiries about food, but Beck is anxious to leave. (Rather than waiting for the evening, the trip begins immediately.)
They go off together in Beck's car but have difficulty making conversation. They try to discuss foreign travel and card games but they obviously have very different social backgrounds. Eventually Beck learns that one of Jane's W.I. associates, Crystal, has just taken a job with Richard Bromley, the local scoutmaster. She reveals that her son Syd was expelled from Richard's scout troop for eating rats. Jane is disgusted.
Jane's husband, Alan, phones her wondering where she is, reminding her that their friend from Yorkshire Henry is coming for the evening. Jane confesses that she's double-booked but doesn't want to say what she's doing. She sees rats scurrying around in some rubbish on the street and starts to feel sick. She asks Beck to stop the car but Beck is enthusing about road junctions and ignores her. Finally Jane cracks, grabs hold of the steering-wheel and crashes the car into a traffic island. The car bursts into flames and Jane runs off into the local cemetery.
Beck phones Jane in great anger but Jane switches her phone off. A stranger approaches Jane and gives her directions for getting back to the main road. Suddenly a horse charges towards them, ridden by Don, who Jane recognizes as the silverware salesman. Don says he was looking for Mr Roaden in Coombe, but in fact DS Worth Roaden has recognized Don as a fugitive and he's on the run again. Don offers Jane the horse and Jane takes it to get home. Don introduces himself to the stranger under a new alias. With Jane on its back, the horse goes crazy and gallops past a local church, where a member of the congregation watches it in awe.
Meanwhile, at Richard Bromley's house, Crystal is sorting out dinner for him, when his mother, Mrs Bromley arrives on spec. Chatting to Crystal about housework and literature, they get on really well. Then the doorbell rings again, and Bess Esoth makes her first appearance. Bess (who has had a sex-change) lives in Blair Atholl, but is on a trip down south. As Richard's scout troop is planning a holiday in Blair Atholl, Bess thought she'd introduce herself to Richard in person. But before Mrs Bromley can fetch him, Jane turns up at great speed on horseback...
Bess manages to stop the horse, and Jane explains what's happened to Richard. Hearing the conversation, Bess realizes they're talking about the Beck she knew from childhood. Knowing Beck's strange habits, she realizes that she needs help, and the group decide to drive up to help them out.
Meanwhile, PC Trafford Barlow is questioning Beck about the crash. And the conversation reveals that he also is a junction-spotter. Then Alan turns up having travelled to Oakwood on the Tube. Then the other five arrive in Richard's car. Beck soon recognizes Bess (or 'Albert', as he was in their youth), and memories come flooding back of a difficult day in Lynmouth. The animosity has remained.
There's a short phone call interlude by PC Barlow, then George Varley turns up on the horse. Then a crucial character makes an appearance - Reverend S. Bury (possibly the brother of Canon Bury from Over the Top), on his way home from church. Bury has heard about the commotion going on in the area, and asks if he can help in any way. Once Jane explains what's happened, Bury knows there's a chance he can sort the mess out.
Bury takes Jane and Beck to one side, and gives a potted summary of his recent sermon on 'forgiveness'. Jane and Beck are both receptive to the message, and decide to put it into action. They return to the larger group.
Jane accepts responsibility for the accident, and Beck forgives her. Everyone is hugely touched. This gives Beck the confidence to apologise for what happened in Lynmouth. And Bess forgives her. Everyone is delighted!
Bury continues home, and Beck, Jane and PC Barlow excitedly run to spot a nearby junction. As the remaining group see how happy they are, they run and join them!
Don then appears under a new alias, collects his horse, and disappears.
Jane is marvelling at how wonderful the day has turned out to be, when she suddenly realizes that Henry will have turned up at their house, finding no-one in!