Let the Rhinos Roll!.After black rhinos begin disappearing on the African Serengeti, the Wild Kratts crew fly there to investigate. After a suspicious rhino stampede, Chris and Martin find a baby rhino that they name Nubs. Martin takes Nubs back to the Tortuga HQ, while Chris continues to investigate the stampede, wondering if there is a connection between it and the disappearances, and if there is something sinister at work. But to Chris' horror, he discovers that Zach Varmitech is behind the whole plot, and is transforming rhinos into his own personal bulldozers. After kidnapping Chris onboard his jet, Zach reveals to him that finding Nubs was a trap so that he could trace the location of the team's headquarters—the Tortuga—and have the rhinos destroy it, with Martin and the Wild Kratts still inside. Faced with their impending doom, the Wild Kratts quickly use the strengths and weaknesses of the black rhino to save themselves, rescue Chris, and both foil Zach's plot.