Young newlyweds Arthur and Jenny Fitton want nothing more than to get their marriage started on the right foot. But before they can depart for their honeymoon in Spain, they have to spend their first night together at the home of Arthur's parents. The couple are prevented from having any intimacy, but it only gets worse. They find out that their trip to Spain is canceled, which sets the tone for a rocky few weeks.

When Professor Willingdon becomes wary of the nuclear weapons he is helping build, he steals a warhead and threatens to detonate it in London in seven days unless the government begins nuclear disarmament. As Willingdon goes into hiding, Detective Folland of Scotland Yard sets out to find him. Willingdon's daughter Ann also joins the cause, hoping she can talk sense into her father before he causes a catastrophe.