During the briefing, converse in any way you like. The mission itself is quite
long. In the icy village, use Aiden to spot a house on the far left side of the
area, where the crew can set up camp. Have Aiden help with the fire, then speak
with Ryan and head outside to make a golden ice cone for him.
Go to the end of the village and enter the hangar with Aiden. Take control of
one of the soldiers and kill the other one near the submarine. The third one
will come look automatically, so get rid of him too. Use the soldier to open
the hangar. After this, go to the submarine and think of a silly, professional
plan. Steer the submarine to the base without hitting and rock walls.
During the interrogation you'll have to decide whether or not you want to talk.
Talking and not talking are both worth a trophy, so you'll need to replay the
chapter either way. Get out of the sub and walk towards the soldiers to see how
you got captured in the first place.
As Aiden, make your way to the end of the orange hall and enter the armory on
the left; kill the guard here. The enter the control room and try to interfere
with the controls; this doesn't work, so take control of him again and fetch
a weapon from the armory, then go back to the control room to kill them and
disable the forcefield. After this, all you have to do is follow the purple line
connecting you to Jodie. Heal her and Ryan, then collect the explosives from
the interrogation room (kill the soldier inside with Aiden).
Make your way through the (red) main hall until you reach a large room with a
pool to dive in the ocean. Suit up and dive down the water to plant the
explosives. First head down the linear path until you reach the condenser
devices. Plant the explosives on each one of them, then head back to the path
(which you can find by looking for the lights in the distance). An interactive
scene starts, which continues when you get back to the base.
Afterwards, the scene extends as you exit the base by running through the halls.
When you've reached the sub, more scenes play and you'll only have to swim to
the surface. Feel free to converse with Ryan in any way you wish.