'Bones' season 12 episode 4 spoilers: What is 'The Price for the Past' for Booth and Aubrey?

A secret from Booth's (David Boreanaz) past gets dug up when a person both he and his wife Brennan (Emily Deschanel) knew turns up dead in the next episode of "Bones: The Final Chapter."

While the previous episode sent the Jeffersonian crew to a retirement home and thus inspired them to think about their future, specifically about having children, the next episode titled "The Price for the Past" will in contrast take main protagonists Booth and Brennan down memory lane, where the path is riddled with potentially hurtful secrets.

The trailer for the upcoming episode further reveals that the case of the week will involve the body of a man tortured to death by the rather ancient method of letting animals feed into the flesh of a living victim. The case forces Booth to look into his past and re-discover a secret that could potentially put his and Brennan's life at risk line.

"This is about revenge," tells his wife in a somber-looking scene before the trailer cuts to the two of them discovering a warehouse rigged with explosives. The two of them barely make it out alive, but they could have potentially sustained serious injuries.

Who would want Booth and Brennan dead and at what cost? What did Booth do in the past that could give anyone a reason to take revenge on him after so many years?

Meanwhile, Aubrey will also be facing his own conflicted past when his father returns into their lives. To be played by actor Guy Boyd, Philip was previously arrested for running a Ponzi scheme, but he eventually got out on bail and flew away to Croatia, leaving the young Aubrey and his mother scraping for money on their own. In "Bones" season 10 episode 22, titled "The Next in the Last," Aubrey claimed to have had a hand in the arrest of his father.

How will the dynamics between the two be like after being estranged for so many years, with all the unaddressed emotional baggage between them? Will the upcoming episode finally see the old and young Aubreys reconcile?

The next episode of "Bones: The Final Chapter" airs on Tuesday, Jan. 24 at 9:01 p.m. EST on FOX.