In “NCIS” Season 14, episode 21, Torres' past haunts him after a murder case is linked to an undercover operation he undertook several years ago. CBS

CBS series “NCIS” is developing the stories of its new characters in Season 14. Episode 20 revealed details of agent Alex Quinn’s (Jennifer Esposito) family. Her mother is suffering from dementia and is worried that she will become a burden to her daughter. Alex decided to move in with her mom in order to take care of her.

With Quinn’s character development out of the way, “NCIS” will now focus on agent Nicholas “Nick” Torres (Wilmer Valderrama). Specifically, the show delves into an undercover operation he did several years ago. According to the synopsis on TVGuide, episode 21 will see Torres rely on old case notes and contacts after a Marine is found murdered. This marine’s death is linked to a former dirt bike gang.

Coincidentally, Torres worked undercover in this bike gang for a year.

READ: “NCIS” Season 14, episode 20 Recap.

The promo of the upcoming episode, titled “One Book, Two Covers,” gives us more clues on what to expect. We see a glimpse of an old photo that shows a younger and bearded Torres posing with bikers. He explains to his team that NCIS had asked him to cover to undertake the undercover operation.

Unfortunately, Torres’ past comes back to haunt him. He reaches out to a contact and this man tells him that even though he has done bad things, he’s still allowed to be a cop.

It doesn’t take long for Gibbs (Mark Harmon) to figure out that his subordinate is hiding something. He confronts Torres in an elevator, “What are you hiding?” It’s something bad because next we see Director Leon Vance (Rocky Carroll) warning him that whatever he plans to do, it isn’t worth throwing his career away for.

We also hear an explosion in the preview of “NCIS” Season 14, episode 21.

“NCIS” airs Tuesdays at 8 p.m. EDT on CBS.