To fix a Los Angeles nuclear reactor that's on the verge of a cataclysmic meltdown, Walter and the team must reluctantly enlist the help of a troubled former member.

A case gets personal for Team Scorpion when three convicts break out of prison and one of them is a brilliant hacker who was forced to help the others steal billions online. Meanwhile, Paige must manage Ralph's expectations when his father returns.

Team Scorpion try to protect Cabe's ex-wife, after she uncovers evidence that suggests foul play in the death of a prominent congressman.

Team Scorpion is tasked with uncovering a mole inside the CIA who is being coerced into stealing deadly chemicals. Paige gives Walter a flirting lesson in preparation for the case.