After winning the Parola Sands motor race in Move - And You're Dead, Alan Tracy tele-calls Grandma, from the parking lot, then drives to her house in his BR2 racing car to collect her. From there, Alan and Grandma head off for a rendezvous with Thunderbird 2 - but their car is hijacked by Victor Gomez and Johnny Gillespie, who force them at gunpoint to drive out onto the centre of the San Miguel Bridge.
Alan and Grandma are then made to climb up onto the girders of the bridge. Then, with a sonic wave generator in place - and an ominous warning for them not to move, or the bomb planted below the bridge will explode - Gomez and Gillespie steal the BR2 and drive off, leaving the Tracys to their fate.
Thunderbird 2 arrives, and using a Neutralizer Tractor, Brains neutralises the sonic wave generator to enable Virgil Tracy to manoeuvre a Jet-Air Transporter on to the bridge underneath the exhausted Alan and Grandma.
Alan finally falls from the girder - but is caught on a cushion of air emitted by a powerful jet engine on the back of the transporter. At Virgil's behest, Grandma jumps from the bridge and also lands safely on the cushion of air. They escape from the bridge, just as the bomb at last explodes. Grandma is then taken back to Tracy Island which then becomes her home.