Phil is stuck in the shower and Mike has to use the restroom. He grabs a crowbar and tries to pry a stuck Phil out of the shower and this reminds Phil of a time in history when Cro discovered the lever.
Cro accidentally invents a lever and tries to show it to the group of neanderthals that have taken him in and just then the saber tooth tiger named Selene attacks the group and she corners Cro on his lever (log). Cro and the log slide down the mountain and he falls into a pond. Cro meets a young mammoth named Pakka and they become fast friends. He says that he wants to be a mammoth too and she is skeptical that he can fit in. First Cro takes her to meet the neanderthals and proves to Ogg that the lever works. Ogg likes it at first until a mishap occurs and Ogg kicks Cro out of the group.
Earle and Mojo are talking about the humans that have come to their valley and want to get rid of them. Ivanna and Phil think that they should invite the humans into the group and Earle and Mojo don't like the idea. Cro tries to use a disguise to be accepted by the mammoths but slips up and they discover that he is a human. Just then Nandy shows up and tells Cro that Ogg, Gogg, and Bobb are in trouble and need his help.
Cro, Pakka, and Nandy go to the cave and find that Selene has the guys cornered. Pakka distracts Selene while Cro climbs up the mountain to use his lever to roll a boulder down on Selene. Pakka is discovered and has to run as she is chased by Selene. Ogg, Gogg, Bobb, and Pakka are now cornered until Cro causes the boulder to roll down and he runs from it. Selene is distracted by the noise and the group runs out. Selene follows them out of the cave and Cro lands on her. Pakka grabs Cro just as the rocks fall on Selene and Ogg is impressed. Ogg takes Cro back into the group.
Doctor C. tells Mike that she knows how to get Phil out of the shower and flushes the toilet and causes the water to turn hot and Phil runs out. Now Doctor C. has to use the restroom and Mike is out of luck once again.