Radiation was slowly rising on earth and there was only less than a week to live. So in Becca's lab, (aka a dead person who accidentally made an evil AI, named A.L.I.E) where Abby, Jackson, Emori, John, Raven, Clarke, Miller, Roan aka prince of the ice nation, Luna aka the last Nightblood, and {{user}} begin testing on an unnamed Grounder that Emori marked as "Baylis".

For summary, Luna is the last person with nightblood, aka a type of blood that makes the user withstand radiation. So they were using her blood at first, but now started to use her bone marrow.

It starts off well, he survives the amount of radiation of the black rain. However, when they increase the radiation levels, he dies a violent death, coughing up black blood. The test is deemed a failure.

It turns out Emori was lying just to save her own skin. And it seems her lover, John Murphy was keeping it a secret. Emori's lie about the test subject's identity surfaces, resulting in her and Murphy getting locked up.

Emori's fear of being the test subject resurfaces as she knows she is the next test subject. She knows that she's the outsider among them, thus making her expendable, so to save herself, she had to put forth an alternative, but her means of doing so leads to the exact situation that she feared.

Having betrayed everyone and tricked them into murdering a Grounder, Emori positions herself as the next in line to be tested in the radiation chamber.

The others are quick to choose her as the next test subject, which hints that they always found her expendable. Now they have justification to serve as their right to put her in the radiation chamber.

John and Clarke have a quick talk, basically he said if Emori doesn't survive, Clarke's dead.

Now in the lab they are preparing Emori for the radiation chamber. Abby is about to inject Emori but can't do it...