Emily Deschanel Plays Temperance Brannan in 'Bones'
Actress Emily Deschanel arrives at the 2014 People's Choice Awards in Los Angeles, California January 8, 2014. REUTERS

"Bones" Season 9, Episode 21 airs on Monday, Apr. 14 on FOX. Titled "The Cold in the Case," this week's new episode tackles cryogenics. Last week's medical marijuana theme is still fresh in many viewers mind. Watch the promo video (FOX sneak peek on YouTube) to see Booth (David Boreanaz) and Brennan (Emily Deschanel) talk about their opposing views again.

Spoiler alert: This feature contains spoilers on Bones Season 6. Episode 21 features Pej Vahdat as Arastoo Vaziri in a special arc. Read at your own risk.

In Bones Season 9, Episode 20, "squintern" Wendell Bray (Michael Grant Terry) confesses to using medical marijuana to ease the pain caused by his bone cancer treatment. Cam (Tamara Taylor) says Bray cannot work for the Jeffersonian anymore. Booth agrees with Cam. But he finds a solution to help Bray.

In Bones Season 9, Episode 21, Cam and Booth face another "reality challenge." This time, things are more personal. Cam is having second thoughts about meeting Vaziri's parents. Booth is up for a promotion that would require him to relocate.

These said conflicts come to the surface as Brennan's Jeffersonian team deal with the murder of a woman whose "body was cryogenically frozen before it was disposed, it will lead them to a cryogenic preservation facility where they will learn more about the victim's personal life."

Read more about Bones Season 9, Episode 21 on ontheflix.com. Watch the FOX-YouTube promo video here, or scroll down to play the video.

Booth's promotion could be related to Danny Beck, the CIA role portrayed by Freddie Prinze, Jr. Bones showrunner Stephen Nathan has earlier said that the characters' lives will change toward (the officially confirmed) Bones Season 10. (Read more about it here.)

WATCH: Bones 9x21 ('The Cold in the Case') | FOX on YouTube

Bones Season 9 airs on FOX every Monday. The network has officially ordered a series renewal. But Bones Season 10 could be the last chapter of the series, according to popular fan speculation. The next new episode, 'The Nail in the Coffin,' airs Apr. 21.

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