Caleb Hass darkest secret is quickly unraveling on Quantico. The next time Mark Raymond enters the picture, viewers will get a major clue Caleb's little side project.

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Last we saw, Caleb had taken his Mark Raymond identity to infiltrate some sort of an organization. Clues from earlier in the series made it seem as if the NAT was going undercover - or returning to - a cult.

"I won't say definitively that it's Scientology, but we definitely want to look at all aspects of sort of all institutions, I would say, that make up America - whether that's religious institutions, whether that's financial institutions, whether that's governmental institutions," Safran previously teased, according to TV Line.

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Perhaps the appearance of Caleb's mother in the midseason finale will help suss out the truth.

"The next piece of the puzzle for Mark Raymond is not next week, but it is coming soon and it is a bigger piece than you have seen in the past," Safran told Entertainment Weekly, indicating that the truth will come after the series' titular Dec. 6 episode.

What do you think Mark Raymond is up to? Sound off in the comments below!

Find out more when Quantico airs Sundays at 10 p.m. ET on ABC.