Thicker Than Water

Ally: Thicker Than Water is an ally quest for Beckett $$

Quick walkthrough
Help Beckett kill the Claw and rescue his brother before it is too late.

Walkthrough
Starting out at the player's C.A.M.P., Beckett recommends to head to the Watoga Underground to find the last of the Blood Eagles' triad of leaders in The Claw. Once there, a conversation with Beckett and Ronny takes place and a key is obtained. Unlock the doors with the key, and follow the linear path through the Underground along with Beckett, fighting past Blood Eagles and their reprogrammed robots, until reaching the Blood Eagles main camp in Garage A. Eventually, one will reach a big red button to open the garage door.

Press the button and kill all remaining Blood Eagles and their robots, including an Assaultron and machinegun laser turrets. Several raiders from Edwin's gang will join and help with the fighting, so try to protect them from being ripped to shreds by the turrets and Assaultron. Afterwards, proceed to confront the Claw in a nearby room, who turns out to be Frankie Beckett. Resolve the situation, either by killing Frankie or convincing Beckett to spare him. Afterwards, return to the C.A.M.P. and talk with Beckett to complete the quest. Beckett will award the Final Word, a legendary 50 cal machine gun, and completing the quest for the first time unlocks the Behind the Curtain achievement.

Bugs
Beckett will fail to recognize that Frankie was spared after returning to one's C.A.M.P.