Note: There's no collectibles to find in these next two segments of the game.
Escape the Horde
Once you take control of Abby again, hold [L1] to sprint and follow the path over to the right, slide down the two icy slopes, then head through the destroyed building. Drop down into the water and follow the path along to the left until you reach an area full of boxes and containers, here you'll want to climb over the fence and continue along until you get saved by Joel and Tommy.
Follow both Tommy and Joel until you reach a room full of gondola lifts and then help push the Gondola up onto the trolley. Here you'll need to work with Joel to take out any Infected that attempt to attack Tommy as he pushes the Gondola over to the window. Once Tommy is done, climb out through the window and follow them into a lodge.
After the cutscenes have played out and you're back with Ellie, follow the path ahead until you reach a fence, go through the gap and enter the lodge. Head downstairs and go into the basement for another cutscene.