Why Bother to Knock

Bill Ferguson, a travel agent in Edinburgh, has an argument with his girlfriend Stella after he loses the key to his apartment. Unnoticed by Bill, Maggie, an American business associate of his, finds his key in his trouser cuff where he had dropped it, but, before returning it, she makes a copy of the key and gives Bill a gift of a case containing several copies of the key with his address on an attached metal tag.

Subsequently travelling around Europe on a business trip, Bill has romantic encounters with three women, giving each one a standing invitation to visit him when in Edinburgh plus one of the keys to his flat. When two of them, plus the daughter of the other, arrive at about the same time to attend the Edinburgh Festival, they all decide to stay with Bill, and Bill has to cope with the women all meeting each other, as well as Stella finding out about them.