Question: ben 10 ultimate alien season 2 last episode
Answer: 32 12 `` Prisoner Number 775 Is Missing '' Dan Riba Peter David April 29 , 2011 ( 2011 - 04 - 29 ) 212 The secrets of Area 51 are revealed to Ben Tennyson by Colonel Rozum after Old George infiltrates and destroys it , setting free the 775th prisoner .