Unwin and Matthew are sent to investigate the sabotage of several desalination plants with the help of Agent Blake.

Unwin and Matthew are on the case when enemy spy George Grey escapes from a maximum security prison and disappears over the estate of Sir Humphrey Barton.

Unwin and Matthew are sent to plug a security leak for a top-secret project.

Unwin is assigned to accompany a bullion train after an attempted robbery.

Unwin and Matthew are puzzled when they're assigned to investigate a security leak regarding an early warning satellite.

Unwin must pose as an army officer in order to prevent the sabotage of an experimental new tank.

When Unwin takes to bed from sunstroke, he has an extraordinary dream. Can he and Matthew survive their dangerous journey in Gabriel, the flying car, and deliver medical supplies to plague-ridden Africa?

Unwin encounters trouble in his parish when a local scientist is held hostage and forced to complete work on a prototype ultrasonic rifle so that mercenaries can shoot down a new jet.

Unwin visits a health farm in order to keep tabs on one of the residents, a notorious spy named Sakov, and is baffled when Sakov manages to engineer the crash of a test car whilst secured in a treatment room.

Unwin infiltrates a gang of saboteurs posing as priests, but will he be discovered before he reveals their nefarious schemes?

Unwin is assigned to protect the King of Muldovia from his brother's assassination attempts. When the flight crew of their plane is incapacitated, Unwin ends up having to pilot the plane himself!

Unwin and Matthew are sent to retrieve two counterfeiting plates from the devious duo of Lord Edward and Lady Martha Hazlewell.