Roof needs to drive the train across the ravine but can't after the Martians accidentally take and break the bridge. A Mecha-Martian team up occurs as they work to make a bridge long and strong enough for the train to cross./The Zee Mobile is great at counting chickens, but when it breaks MacBarm's barn door, it is up to the Mechas to build him a new one by figuring out what material could hold against spontaneous crashes.