When Sumsy and Travis decide they need a machine shelter too, Spud steps in to help. But each time they think they've gathered surplus materials from the old willow tree, they need to share them with Bob for various new building projects. Eager to have a shelter, Sumsy must find a new way to get the materials she needs! Bob and the can-do crew are working on a very exciting job - a bridge - and Bob has promised Scrambler he can be the first machine to ride across it. Desperate to get the job done as fast as possible, Scrambler rushes off - while Dizzy struggles to keep up, skidding off the path and into the river. Can Scrambler save her without slowing everyone down?