*Spoiler Alert*
Story related and cannnot be missed.
*** Spoiler - click to reveal ***After you search the small cabin by the bridge a group of walkers will come to your group. The group decides to go up the mountains to the ski resort. After the cutscene you arrive at the ski resort and have to climb up a pole to see if people are following you. When you climb down you will see your group arguing with another group of people. When walking towards them you realise its kenny with some other people. They will let you in the ski lodge. A cutscene will start and the achievement will unlock.