Episode three of "The 100" Season 4 was a failure for Bellamy (Bob Morley), Clarke (Eliza Taylor) and Jaha (Eli Goree). The trio's quest to find a fallout shelter failed, while Abby (Paige Turco) was also unsuccessful in saving Luna's (Nadia Hilker) people from acute radiation poisoning. Fortunately, Luna survived the poisoning because of her nightblood.

Episode four titled "A Lie Guarded" will follow Abby, Luna and the other Arkadians as they try to create a cure or vaccine by synthesizing Luna's radiation-immune blood, TVLine reported. The group will travel to Becca's (Erica Cerra) deserted laboratory, which houses what they need for the plan.

Abby's medical expertise will be a huge focus in Season 4 of "The 100." Clarke, meanwhile, is having problems grappling with the difficult decision she made.

She has already picked the 100 individuals who will inhabit the Alpha Station if she doesn't devise another plan before the acid rain and radiation fallout ensue. Jasper (Devon Bostick) is angry over Clarke's picks, telling her that she isn't God to decide in such a life-and-death matter.

This is a huge burden for Clarke even though technically, she's not her people's elected leader. Despite that, Clarke is always the one who keeps them safe and is tasked with making the hardest decisions.

Monty (Christopher Larkin) and Harper (Chelsey Reist), meanwhile, couldn't catch a break. They may have decided to cement their relationship but their problems aren't coming to an end anytime soon.

It's interesting how Monty will deal with the oncoming tragedy; the man is always considered as the toughest and most principled out of the 100 young people sent to the ground. Check out photos from "A Lie Guarded" on TV Fanatic.

"The 100" writers recently teased the remaining episodes of Season 4. The writers' official Twitter page likened the first three episodes of the season to "delicious appetizers before the scrumptious, hearty steak dinner" of episodes four to six. Another tweet revealed that "A Lie Guarded" will be "brutal" and challenging for the characters.

Next week's #The100, "A Lie Guarded," is brutal. Some characters you hate will be liked and some you like will be hated... It's a tough one.

— Inside The 100 (@InsideThe100) February 16, 2017

A Season 5 renewal is highly likely for "The 100." The Cancel Bear, which tracks low-rated TV shows' performance, is confident that the series will be renewed due to its consistent ratings. Its first three episodes of Season 4 generated a 0.4 rating in adults aged 18 to 49. The show's Season 5 renewal could be announced by May 2017.

Watch the promo for "A Lie Guarded" below. The episode airs on Wednesday, Feb. 22 at 9/8c on The CW.