Lynne is on the bus with an unnamed friend. The friend tells Lynne that she was right and there are three people in her marriage. As the friend starts crying, Lynne asks her why she thinks that. Her reason is the present her husband bought last week, which is a 3 person bicycle.
Lynne and her friend are on the bus, probably on the top deck. It is busy so that would suggest it is either commuting time or a busy Saturday afternoon. The man at the front is deaf or a doctor. At first glance, one might think he was listening to his ipod, but this being 1982, ipods were not invented, and neither were in-ear ear phones. So in his ears is either a hearing aid, one of the massive ones which is attached to his belt, or a stethoscope. He has a doctor's look about him and perhaps it is a new stethoscope which he is quite proud of. If he was listening to his ipod, it would either be a Radio 4 podcast or Brahms.
Lynne's friend is unhappy, and she has every right to be. Her husband has not only bought a three person bicycle but invited another woman along. This is certainly not an affair he is trying to keep secret. Even though the husband is seeing another woman, he is inviting his wife along too. What is he trying to achieve? Is it because this other woman wears more revealing clothes? Is she a better cycler? Is she a better navigator? Maybe he just likes cycling on a tandem so much but his ability to lead and look where he's going is so poor that he wants someone else to do it. His wife is also pretty bad at these things so it is essential that he invites another woman along.
If Lynne's friend's husband is only using this woman to help with the cycling then she has nothing to worry about. If he starts inviting her on holiday and buys an extra large bed then she should start worrying. Or perhaps if she stops showing up then the friend should start worrying more. He'll want to keep it a secret if the affair escalates, but then he's more likely to cycle into a ditch.