Whilst collecting monies for overdue library books Timothy stumbles upon married building tycoon Byron Hadlee with his mistress. To keep him quiet Byron gives Timothy a thousand pounds, causing him to quit the library, and an invitation to a party where Timothy loses his trousers but, thanks to Mother, not his job.
Timothy is named in the will of his late uncle Barstable but his reward is in a secret drawer in a sideboard and nobody can find the key. During a concert at the wake the key is eventually located but when Timothy finally opens the drawer he is surprised at the nature of his legacy.
Timothy is shocked when chief librarian Endicott suggests that he takes early retirement. Inspired by sister Muriel Timothy attends the Endicotts' party to prove his usefulness and, when the family cat gets stuck a tree, Timothy shows himself to a branch librarian in the literal sense - getting his job back, though not quite as expected.
Timothy is challenged by new girlfriend, barge-dwelling Fenella, to leave home and come away with her but first he has to attend a family christening, to which he has accidentally brought a duck. The ceremony over Timothy finds that Fenella has predictably gone without him, leaving him a bizarre inflatable monster which wrecks his mother's car.