Young Tom Dawes is enthralled by the sight of a fine schonner sailing up the Avon Gorge. Soon he and his father become mixed up in the mystery of a missing girl, a half recorded message, and intruders at Bristol Docks...

The adventure continues as Sid Dawes finds the runaway girl, Lynn, and Tom learns more about the mysterious recorded message. Trouble is looming for them all: the villainous Colonel Gaines has become suspicious - and he's a dangerous enemy.

Chased by the men from the sailing ship, Tom and Lynn find an unusual refuge. Aboard the Patriot, Bert makes a frightening discovery.

Tension mounts as Tom tries to find where Lynn's kidnappers have taken her. Confronted by Colonel Gaines, she receives a clue to the mysterious recorded message...

With Southways now out of the way, Gaines' men turn their attention to Lynn. Young Tom picks up the trail at last...

Tom and his father are getting ever closer to finally solving the mystery of Lynn's disappearance...

Sid and Tom chase the evil Colonel Gaines, who is carrying captives aboard his sailing ship.