On a junk collecting expedition Amber and Sam see a large object land on Junketir. They drive their Dustbug towards it, but realise it is further away than they thought. They worry that they haven't enough fuel to return to base. The children know that they use more fuel on rough terrain than on a road but the route over rough terrain is shorter. They try to work out the best way home, and Numberella helps to analyse the problem and choose the safest option, which surprises them.