Crablogger 1, a huge tree-felling machine, arrives at base camp in South America in preparation for its first mission. In the evening the base commander (Jansen), takes the crew for a meal at a local restaurant in nearby San Martino, as they are not due to start work until the next morning.
When the Crablogger sets off from base camp, both Peterson and McColl collapse, the victims of food poisoning, and the Crablogger veers off course heading straight for San Martino.
A Path of Destruction
McColl was unable to get to the remote switch in time before he passes out, leaving the Crablogger in automatic mode. To make matters worse the vehicle has to be constantly relived of the supplies of wood pulp that it produces while in motion, for if the machinery jams the resulting explosion of the Superon-fuelled atomic reactor would lay waste to everything within a 50-mile radius. The one way to stop the huge machine is to active the secret reactor shut-down procedure from inside the control cabin, which can be accessed only through the roof of the vehicle.
Only One Outfit Can Handle This Situation
Jansen calls International Rescue and Scott sets off in Thunderbird 1, while Jeff apprises Lady Penelope of the situation.
Shut-down Procedure
Lady Penelope travels to Jim Lucas' House and gets him to give her the shut-down procedure, she transmits the information to Brains which she had stored on her Micord-4 recorder.
Shut-down
Virgil and Brans, arrives at the danger zone, and set off in the mobile crane, driven at top speed by Scott. The crane catches up with the Crablogger and Scott lifts the boys onto the roof of the Crablogger. Virgil gains access to the control cabin by cutting through the roof. The vehicle is now heading straight for the San Martino Dam Lady Penelope transmits Lucas's information and Brains activates the reactor shut-down.
Time-lag!
There is a three-minute time-lag before the machine will actually come to a halt, the Crablogger is now moving along a narrow mountain track towards the Dam. They set about draining the tanks of the explosive Superon fuel. Scott brings up a fuel truck and Virgil and Brains attach siphons to the fuel outlets.
The End of the Crablogger
The Crablogger finally stops, but the ledge is crumbling away beneath its immense weight. At the last minute, with the tanks finally drained, Virgil and Brans leap clear as the Crablogger, as it falls from the cliff path. The machine is completely destroyed, but the Dam is saved.
