John is bird watching with his father. Susan Fraser has found herself cut off from land so John helps her. Reaching land she hands him a note explain from his father has gone. Nobody now seems to know his father as he heads out by boat
John and Susan go to the police to help look for his father. The police won't intervene, as Tom Corby is suspended from Scotland Yard. Tom Corby and his two contacts meet up with Kessler. Police surveillance believe Corby is on the take.
John and Susan catch sight of his father but are unaware that hit man is assigned to stop them. Tom Corby wants him the hit man stopped but the police are closing in. A motorcycle driver has been hired to cause an John accident.
John and Susan realise they are being tailed by a motorcyclist but he out smarts them. John is angry when Susan talks about returning to Scotland again. When John gets too close to seeing his father the pair get trapped underground.
John and Susan find themselves trapped underground. Tom refuses to leave the Falcon pub unless he knows his son his safe but Bowers has conned him. With his father long gone, John and Susan finally reach an exit to the surface.
Susan finds a rope to help John but the motorcyclist is still in the area. A friendly garage attendant they discover the group holding John's father bought a map of Ullswater. The pair get a canoe and attempt to out flank the gang.
John and Susan need rescuing from the lake. With Susan receiving hospital care, John learns his father is using an alias. The pair head for the high ground and hear Kessler target shooting. Moving for a better a look the pair are spotted.
The biker forces John and Susan to go high up the mountain. As he makes a grab he falls off the cliff. He is badly injured so John leaves Susan to get help. Delirious the biker says "meet at Grassington" but the John car has been disabled.
Tom warns off John with Bowers close by. Bowers takes Kessler to the airport to show him the target. John and Susan overhear Selby revealing information to his father. John decides to take a photograph of Kessler to prove to the police.
Tom finds the man, who fit him up, is in charge so asks for a deal. He knows Bartas is their target and wants in. Susan comes to John's rescue when Kessler hears trying to take a photo. He does find the hit will take place in Edinburgh.
John sees Kessler preparing his sniper's rifle which puts the youngsters in grave danger. Tom gets warned about asking questions. With the Tattoo drowning out the noise, John and Susan search the castle looking for Kessler's sniper nest.
Bartas is struck by a sniper's dart. Bowers pretends to be a doctor, pronounces heart attack and whisks him off in an ambulance. John stays in pursuit while Susan tells the police about the kidnapping. Tom realises Bowers wants him dead.
The police discover the stolen ambulance and close in. Bartas is moved to Morrison boat but Tom makes a run for it before he is killed. He is thwarted by John's capture but by the time the gang reach the boat the coast guard are on alert.