"Among Us Stalks The Sentinels"
The X-Men are off for some much needed and well deserved rest after beating the Juggernaut, but as they leave they are threatened by a new menace. Dr. Bolivar Trask is stoking the winds of fear in humanity about the Mutant Menace as he debates with Professor Xavier on national TV where he shows his new weapon to protect humanity, the Sentinels. But they turn on their master, declare their autonomy, kidnap Trask and bring him back to their leader, Master Mold. The X-Men, in pursuit, arrive at the secret lair of the Sentinels.
First appearance of the Sentinels and Bolivar Trask.
Story reprinted in X-Men (1963) #68.