"Plan B" is the Chapter 6 story mission in Borderlands 2. You get it after completing the mission The Road to Sanctuary.
Contents
Objectives
Get key to Roland's Command Center
Unlock Roland's command center
Description
Story Mission
Optional: No
Locations
NPCs
Enemies
Mission Briefing
Roland is missing. With their leader gone, the Crimson Raiders of Sanctuary are helpless. Roland left specific instructions with the town mechanic, Scooter, which were to be carried out in the event of his disappearance. Scooter has asked you to help him carry out these instructions, which entail getting Sanctuary - which, if you're keeping score, used to be an old mining spaceship - airborne and out of Jack's reach.
Mission Debriefing
Reward
Money and XP