Tankor's villainy escalates quickly as he decides to use the Key to Vector Sigma to turn the Maximals into pure metal! Meanwhile, Optimus and company drill for water for their new garden and get some kind of primordial ooze instead! Can the Maximals use that to cure Nightscream when he gets hit by the Key? Just what is this Key, anyway? And will Optimus and Cheetor stop bickering like an old married couple before Rattrap just kills them all? Find out this week as we watch The Key!