 Paul Steppe, a watch repairman, suspects his wife is cheating on him while he tends to his store every afternoon. Consumed with jealousy, he devises a time bomb set to go off at four o  clock - the same time her "lover" pays his daily visit. One day, when his wife is at the market, he sneaks into the house to plant the device. There, Paul is surprised by two burglars, who tie him up and gag him - leaving him at the mercy of his own device ticking away. With an hour to go, his wife comes home and Paul overhears her talking to her "lover". Apparently he turns out to be her brother Dave, who was recently released from prison. Deciding to reveal her secret to Paul, the two leave for his store, leaving Paul alone with the clock ticking away.