The Missing Link

 is a quest in Fallout 76. Although completing this quest is not required to unlock Signal Strength, reaching the Top of the World will unlock it and branch off the main quests.

Synopsis
After joining the Fire Breathers and realizing they were all wiped out, the only clue left is to follow Hank Madigan's trail, who disappeared among the raiders of Pleasant Valley, trying to set up an uplink...

Walkthrough

 * Reach the Top of the World located in the center of the map.
 * Complete the quests Signal Strength, Flavors of Mayhem and Key to the Past.
 * Grab the Broken Uplink in the Raider's Cache.
 * Hack the terminal at Abbie's Bunker and head in.