Mod:Fallout: The Frontier/I Am Legion

Praise the Lord and Pass the Ammunition! is the first main quest in the Crusaders quest line, typically given during A Bridge Too Far.

Detailed walkthrough
Upon exiting Camp Phoenix and heading north one will meet Esther, a Crusader recruit. Esther will offer to buy you a few drinks at The White Rabbit Hole. After a brief chat one can either ask Esther to take you directly to RobCo Tower or opt to check out the place by themselves later.

Talking to Warden Howell outside RobCo Tower will end this quest and start There's a Power Greater than Atomic!