Note: The mission is acquired immediately after dealing with the genophage and is triggered by the first visit to the Citadel after that, thus causing all uncompleted Citadel-related side-quests to expire. See the preparatory notes on Priority: Tuchanka for details. Likewise, Priority: Citadel II itself is a "point of no return" for Grissom Academy: Emergency Evacuation, which must be completed prior.