Grandmaster Glitch is visiting London and spots the perfect souvenir at a riverside stall - a majestic hat that was clearly made for a Grandmaster! But when he finds he has no money, he decides to raise some by working as a tour guide on the River Thames. The Go Jetters are also visiting London while Lars helps to fix his favourite his bridge - Tower Bridge. Ubercorn explains that this amazing bridge can be raised to allow tall river traffic to pass safely beneath. While Lars goes to fix Tower Bridge, Xuli, Kyan and Foz jump onto a riverboat tour, unaware that they are in fact boarding Grim HQ! Before they can jump ship, Glitch sets sail, giving out his very own glitchy facts and spending his customers' money on his Union Jack hat. But when the hat blows away in the breeze and Glitch gives chase, he puts tourists, boats and Tower Bridge itself in danger.

Glitch is excited when Lars refits the Grimbler with new, clean biogas boosters that could make it even faster than the Vroomster! The boosters run on gas made from food waste, and luckily there is plenty of leftover food in the academy canteen for the Grimbots to gather up. But Glitch overloads the boosters and BOOM! He loses control of the Grimbler and is sent flying across the academy, out of control. Lars leads the Go Jetters into action by giving chase across land and sea in the their all-action vehicle, the Truckster. But with the runaway boosters zooming towards Ubercorn, the Grimbots and the academy, the Go Jetters need click-ons to stop them!