It's Not That Simple

Picking up as Eve's shield fails on Mars, the Guardians fight to hold off the Sequids until Robot's EMP device buys them an escape. Cornered by the Martian Emperor, who demands Shapesmith be handed over for execution, Mark answers only with a quiet acknowledgment before commandeering a ship and blasting through the pursuing Martian fleet to get everyone home. Back on Earth, a bloodied Rex survives a point-blank shot from King Lizard and beats the would-be tyrant to a pulp before the GDA arrives to find a horrifying secret hidden inside a body.

Grief settles over the team as Dupli-Kate is laid to rest, with The Immortal taking her death especially hard. Debbie rejects Cecil's overtures and instead hires April Howsam, a GDA member, purely as a tutor for the fast-developing Oliver. Mark reconnects with a distant Amber, checks on a recovering Rex, and watches Rick struggle with the trauma of what Sinclair did to him. Seeking advice about his relationship, Mark visits Art, and a clever intercutting shows Mark and Amber voicing the same fears in separate conversations without ever saying them to each other.

Art hands Mark a collection of Nolan's books, which turn out to be coded accounts of the legendary Space Racer and his mind-controlled weapon, and of savage beasts called Rognarrs, both threats capable of harming Viltrumites. Mark realizes these could be keys to the coming war. Allen the Alien then arrives on Earth, briefly mistaken for Omni-Man by The Immortal, and shares grim news about Nolan's imprisonment before taking the books to research. Elsewhere, Kregg berates a silent Nolan in his asteroid cell, a lone Sequid reattaches itself to Rus Livingston, and a newly-composed Angstrom prepares to pay Mark a visit.

The Guardians escape Mars, and Rex Splode survives a head wound to defeat King Lizard, revealing Shrinking Rae hidden within Komodo Dragon. Dupli-Kate is buried, and the team grapples with fractured morale. Mark receives Nolan's coded books introducing Space Racer and the Rognarrs.

Allen returns to Earth to update Mark on Nolan's captivity and leaves with the books. Rus Livingston is quietly reinfected by a surviving Sequid, and Angstrom Levy resurfaces, poised to strike at Invincible.

Unlike her comic counterpart, Shrinking Rae survives her ordeal with Komodo Dragon. Rex proves unusually durable after being shot in the head, hinting he was experimented on much like Eve. The coin Eve once made for Val appears again, still improbably in circulation despite being worthless.

A brief shot of coffee forming broken hearts foreshadows Mark and Amber's eventual split, while Eve's affectionate hug plants the seed of a future romance. Rick Sheridan is now voiced by Luke Macfarlane, and Angstrom returns after vanishing earlier in the season.