While working undercover for 20-Squad, Alfaro encounters associates from a previous undercover case in Long Beach, embarking on a dangerous mission that stirs up unresolved issues from the past.

When violent robbers loot a museum vault, fleeing with almost a billion dollars in treasure recovered from a sunken ship, Hondo and 20-Squad must chase down the thieving killers before they flee the country. Meanwhile, Tan reckons with the fallout from a SWAT Academy accident, and Gamble nervously awaits the verdict of her IA investigation.