Team Scorpion continues to work with their nemesis, Mark Collins, in order to prevent an extinction event that could end humanity. Also, Cabe's last-minute decision while on the case leads to the possible end of his career.

While decommissioning an old nuclear missile, a simple accident causes Team Scorpion to endure exposure to toxic vapor while trying to prevent the nuke from detonating. Also, Paige confronts Happy about constantly tagging along with her and Walter.