Knut Haukelid (the Jason Bourne guy) is still recovering from his accidental shooting, and he's still pretty miffed he couldn't parachute into Norway.
He gets offered a second chance, though, because the Allies are pretty desperate to destroy the Vemork plant. (While it still functions, Hitler has control of the world's supply of heavy water, which is far more efficient at slowing down neutrons to create a chain reaction than graphite.)
The new plan, called Operation Gunnerside, is to parachute Haukelid and five other Norwegian volunteers onto the Hardanger Plateau where Jens Poulsson and his team are still camping out (poor guys). Then they'll all ski to Vemork, break in, and blow up crucial machines in the plant's basement.
Col. Wilson, the same guy who led the disastrous previous attempt, makes it clear to Haukelid and his team that the Germans aren't following anyone's rules and will definitely kill them if they get caught. (This is probably just what the guys want to hear.)
Because of this, they're issued cyanide tablets to keep in their mouths and bite down on in case of capture. Yup, that "death pill" you've seen in the movies is a real thing.
Team Gunnerside parachutes into Norway in February of 1943. But when they land, it's clear they aren't on the frozen lake they were aiming for. Before they can find Poulsson's team, though, they get trapped in a cabin during a blizzard that lasts five days.
When they finally get to go out and look for the other team, they encounter Claus Helberg and Arne Kjelstrup. After they almost shoot each other, they have a back-slapping reunion.
They decide the best way to get into the plant is through the only weak point in the German defenses: They have to climb down a gorge, cross a river, and climb up to the plant from below.
Ronneberg will lead the five-man demolition party, and Haukelid will lead a five-man covering party.
If the plant's doors are bolted, the demolition team will crawl in through an air duct.
They all agree that if anything happens, they'll carry on the plan, no matter what. And if captured, they vow to take their own life. This is serious business.