Paul and Steve are called upon to crack a case involving Carl Milbourne, the brother-in-law of wealthy financier Maurice Lonsdale. After the news that Carl has perished in a fatal car accident, rumours begin to stir that despite all odds, Carl is alive and well.

When Maurice's widowed Sister Margaret pleads for the crime-fighting duos help, Paul and Steve find themselves on a trail of deception stretching from London to Switzerland. Their lives are in grave danger as everything is done in an attempt to stall their search - anonymous gunmen, exploding cars, ransom demands, and a mysterious rendezvous that may prove to be the end of Paul and Steve...