A piece of mysterious white wall is found deep underground, causing an accident at the mining site of the world's largest final depository for nuclear waste. The director of the project, Lars Rapp, wants to keep the find a secret, but rumours spread quickly in the small boom town that has sprung up around the site. Also, an environmental activist was found flying a drone above the mine just before the accident. She may have dropped something dangerous on the site, maybe even a bomb?

The mining company Ecso has to issue a public statement about the accident at the site before rumours get out of hand. However, Lars does not know what they have found deep underground and, while at the headquarters in Stockholm, gives the explanation they want to hear: the accident was caused by a mistake made by Holmström, the charger who lost his life.

Lars reveals the white wall to Said to explain the situation and why he had to lie about the cause of the accident. Said is excited about the mysterious glowing object, but Lars asks him to hold the horses: Lars already has a strong theory about what they’ve found underground.

Since Helen’s wall samples failed to reveal what the wall is made of, Christopher, Helen's professor, arrives to help. He is an acclaimed scientist, but also a controversial character. Both Lars and Christopher are used to being the heads of their respective turfs, and are at odds right from the start.

It's the day of the opening ceremony of the waste disposal facility. Lars is doing his best to smile as he goes through the ritual of clinging glasses with Gina, other Ecso staff members and the guests. All the while knowing that the tunnel in which they are about to begin storing nuclear waste also house a mysterious capsule they still know nothing about.

Helen and Magnus face a mind blowing scene as they come to work in the tunnel. The ceiling of the cave has collapsed. The curvy shape of the capsule is visible now, it looks like a Zeppelin that has landed vertically deep underground, just like Christopher estimated.

With a heavy heart, Helen meets Gina and tells her everything about the capsule and what's been going on at the site lately. And that Lars is trying to open it as they speak. Doing this, Helen feels horrible but she wants to protect Lars from himself and his fixation to open the capsule.

Astrid takes Lars to a cabin, and go skiing through the wilderness. From the top of the fell they can see all the way to the mine and start to head towards it. Astrid is giving Lars directions and advise how to avoid getting caught by the guards and how to get in to the facility area.