Help Will Come Tomorrow

This will require you to complete the game with all of your survivors alive (unlocking "No man left behind") and by completing the final "story" quests that unlock during the night phase of day 23 or 24. Your survivors will automatically talk about help coming and how they need to prepare. You will then have two quests to setup beacons at both ends of the train track by sending out expeditions with the materials needed to build the beacons equipped. The tiles will be marked on the map for where you need to build the beacons and the event to build them should be triggered by moving to the tile. Both beacons need to be setup before the end of day 25.