Kovich chairs a meeting to discuss first contact with Species 10-C.

Stamets reports to Burnham, Rillak, and Vance that the new DMA controller is significantly more powerful than the one Tarka destroyed. Their one-week window is now 12 hours. Burnham says she'll be ready to go in 2 hrs.

Rillak intends to join the mission.

Book intends to drop Tarka off at a nearby inhabitable planet. Tarka talks his way onto Book's mission to destroy the new DMA at its source in Species 10-C's hyper field. Tarka informs him that he'll need programmable anti-matter and he knows where they can get it.

Saru bids Bryce goodbye as Bryce is working with Kovich on communicating with 10-C and won't be joining Discovery on its mission.

Saru sees T'Rina and asks to take her up on her dinner offer. He shares his feelings for her but she is called away before she can respond.

Adira returns to Discovery.

Burnham and Rillak talk before the mission.

Burnham addresses the ship, its crew, and the delegates, and then Discovery jumps.

They arrive nine lightyears away from the galactic barrier which is five more than Stamets had estimated.

Saru is sent to tell the delegates that the warp trip will take longer and discovers that T'Rina is on board as the Ni'var delegate as their official delegate didn't arrive in time.

Culber counsels him over his insecurity.

Tarka's leading Book to the programmable anti-matter stash when Book sees a tower that means they're approaching an Emerald Chain work camp. Tarka insists that it's out of commission but Book insists on getting the whole story.

Tarka recounts how he was captured ten years ago and put in a lab with another scientist named Ourous. After a year, they became friends.

Discovery arrives at the galactic barrier. There's more negative matter than expected so Stamets and Zora decide the best plan is to ride a spatial cell "bubble" through the barrier.

Rillak arrives with an urgent message.

A courier scavenging vehicle spooks Tarka and Book. Tarka remembers when Ourous told him about an interdimensional target he wanted to escape to. Ourous invites Tarka to come with him.

Vance's message is that the DMA has moved into the Alpha Quadrant, with Ni'Var and Earth in the impact zone. Rillak and Burnham argue about whether to tell the crew.

The ship's cell has stalled and they are stuck. Stamets believes that moving to another cell that's on a current, they'll be through the barrier quickly.

Tarka and Book find Tarka's old prison lab. The stash is there, although part of it was used for the transporter they used earlier than expected. Their power wasn't enough and their guards caught them. The guards reveal that Tarka was put in with Ourous to find out what he was secretly working on. Tarka fights off the guards and removes the Emerald Chain tags from his neck and Ourous's.

Ourous refuses to let himself slow Tarka's escape. He promises to fix the device and they can travel to Kayalees together someday. He insists Tarka escape without him. Tarka believes that Ourous managed to escape to Kayalees a few weeks later.

Discovery moves from cell to cell to reach the target stable cell to carry them through the barrier. It's tense.

Rillak and Burnham talk again.

Tarka and Book talk about Tarka's choices and guilt.

Discovery makes it through the barrier. Rillak addresses the ship and lets them know about the DMA.

Saru seeks out T'Rina to express his sympathy for the news about the DMA threatening Ni'Var.

Rillak and Burnham consult on how to approach the 10-C hypershield. Burnham shares that she has faith in Rillak.