Supernatural's Dean Winchester disappeared from his brother's life for a few months as a teenager and Sam will finally find out why in "Bad Boys."

When Dean (Jensen Ackles) gets a ghost hunting related call from an old friend named Sonny (Blake Gibbons), the Winchester brothers travel to a home for delinquent boys. Unbeknownst to Sam (Jared Padalecki), the home was briefly visited by a teenage Dean after he was caught steeling food.

As the hunters attempt to deal with a murderous ghost, Dean flashes back to his past and Sam tries to persuade him to fill him in on the story.

'Supernatural' Season 9 Spoilers: Shocking Secret from Dean's Past Stuns Sam, Flashback to Young Winchesters in 'Bad Boys' VIDEO

A new sneak peek (see video below) gives viewers a quick summary of where Dean went, but saves the flashbacks for later.

Left alone with a young Sam, a 16-year-old Dean lost their food money in a card game. Knowing they still had to feed themselves for a while, Dean attempted to steal food from the market but was picked up by the police and sent to a boys' home. When John Winchester returned from hunting a rugaru, he told Sam that his brother was off on a hunt and shipped him off to Bobby's for a few months.

However, just as Dean shares this nugget of truth, he transitions directly into checking up on the angel that is secretly inside his brother.

'Supernatural' Season 9 Spoilers: Dean's Secret Past Revealed First Look PHOTOS, Young Winchesters Flashback in 'Bad Boys' VIDEO

"Dean is continuing to lie to Sam, and he's hating it every step of the way," Padalecki told TV Line over the summer. "And Sam can't really tell. Sam's like, 'OK, I remember our conversation about teamwork, so I'm going to take you at your word.' But when Sam finds out, s--t's going to hit the fan."

Find more information regarding the upcoming flashbacks to young Dean here and new promo photos for the episode here.

Supernatural airs Tuesdays at 9 p.m. ET on the CW.