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.
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...
|-|| ||Follow Madigan's Trail|
|-|| ||Complete Rose's quests to gain her trust|
|-|| ||Retrieve the uplink|
|-||Go to the Free States Bunker|