"Suddenly... the Sub-Mariner!", The Scarlet Witch collapses after the battle in the previous issue; Black Widow steals an experimental jet from General Ross; Meanwhile, the Sub-Mariner attacks a submarine destroying underwater wildlife, then decides to attack the base it came from; The Avengers receive a call from Captain America, warning that a dangerous item called the "Cosmic Cube" has been spotted near the base and the Avengers should secure it; Quicksilver stays with the weak Scarlet Witch and the Avengers arrive at the base and battle with Sub-Mariner, where Hercules unwittingly mentions the cube to him; The Sub-Mariner flees, returns with the cube and the battle starts again. Avengers roll call: Hawkeye, Goliath, the Wasp, Quicksilver, and the Scarlet Witch. Captain America appearance. Letter to the editor from writer Steve Utley.
