Uncanny X-Men (Marvel, 1963 1st Series) #59
Cover pencils by Neal Adams. Do Or Die, Baby!, script by Chris Claremont and Roy Thomas, pencils by Neal Adams, inks by Tom Palmer, colors by Neal Adams.
With Larry Trask revealed to be a mutant, the Sentinels refuse to obey him any more as they continue to capture mutants and prepare to kill them.
