Police inspector Lanz has long been trailing a serial killer who strikes while on vacation and loves to needle him with words "Wish you were here" on a postcard. When the killer turns up in London, Lanz takes up the chase, but before he can nail his suspect, the man falls to his death from a rooftop. The case is closed, Lanz goes on a vacation to Vienna with his lovely wife Karen, not knowing that there is already someone waiting for him...