Arriving from Dimension Aqua for a rendezvous with Aquaman, Queen Mera is, instead, met by Aqualad. Aquaman soon passes by, but ignores them, as they call out to him. Aqualad and Mera start to pursue Aquaman, but he waves them off. Suddenly, a strange alien girl surfaces next to Aquaman. Mera is crestfallen that Aquaman would choose to spend his time with the alien over her, but tearfully respects his choice. Aqualad, however, urges Mera to go after them, citing that Aquaman would never treat her so poorly. Mera uses her absolute command over water to ensnare Aquaman in a hard water lasso. The alien girl, though, also possesses abilities similar to Mera's. She reconfigures Mera's lasso construct into a giant hoop, that she then sends barreling at Aqualad and Mera. The pair are caught up within the hoop, momentarily, until Mera uses her powers to dissipate it. Mera then forms an extremely hard water tunnel that leads straight to Aquaman. Mera and Aqualad race to span the distance to Aquaman, but the alien uses her power to raise the tunnel high into the sky. By the time Mera can finally dissipate the tunnel, she and Aqualad have ascended so far above the surface of the ocean, that the fall back down will kill them. Mera pulls hard water gliders up out of the sea, to allow them to descend safely back down into the ocean. They decide to try a more stealthy approach to getting Aquaman back. Just as Mera is about to ambush the alien girl, she witnesses Aquaman's startling transformation into an alien, too.
Mera launches her attack, taking the alien girl by surprise, imprisoning her in a hard water cage. Mera demands the alien return Aquaman to normal. "Aquaman", though, turns out to truly be an alien. The pair of aliens, Rovere and Sirene, are sibling shape shifters. They crash landed on Earth, while trying to escape from an alien criminal gang. Rovere had run with the gang until Sirene convinced him to go straight. Now the criminals are in pursuit of Rovere, to stop him from going to the authorities on their world. The first Earthling Rovere encountered was Aquaman. Rovere imprisoned Aquaman within a cave, then assumed his identity to throw the alien criminals off his trail. Mera departs to free Aquaman from his imprisonment. Before she can return, the alien criminals arrive on Earth, quickly spying Rovere and Sirene with Aqualad. Clawed tentacles erupt from the alien vessel, capturing the trio. Rovere and Sirene escape by transforming into eels, abandoning Aqualad to his alien captors. The aliens interrogate Aqualad as to the whereabouts of Rovere and Sirene. When Aqualad fails to provide any information, the aliens prepare to kill him. Aquaman bursts from the sea, riding the crest of a wave created by Mera. They just about have the trio of alien criminals defeated, when the clawed tentacles erupt, once more, from the ship, capturing Aquaman and Mera, as well as Aqualad, again. The aliens believe Mera to be a shape shifted Sirene, as, to their awareness, only beings from their world can control & manipulate water the way Mera does. They demand Mera give up the whereabouts of Rovere, or else face execution. As they take aim with their weapons, enormous, monstrous crustaceans emerge from the sea, scattering the aliens. Their attack damages the alien vessel, inadvertently freeing Aquaman, Aqualad and Mera. Their freedom is short lived, though, as the creatures scoop up the heroic trio in their gargantuan pincers, and return to the sea.
The giant crustaceans turn out to be Rovere and Sirene. The rescue was the least a guilty Rovere felt he could do, for involving Aquaman in his troubles. Sirene's motivations though are entirely romantic, which raises Mera's dander. Aquaman steps in, quickly, to defuse the situation before it can escalate into violence. With the heroes thus distracted, Rovere swims away, back towards the alien gangsters. Aquaman, Aqualad, Mera, and Sirene race to intercept Rovere before he can reach the shoreline. Rovere has too big a lead, though. As he emerges from the surf, the aliens prepare to shoot him. Mera and Sirene hurl hard water spheres at the aliens, disarming them. The alien criminals grab Rovere, forcing him back into their ship. They rush to depart before the heroes can reach them. Mera & Sirene create a stream of water, reaching from the ocean to the hatch of the alien vessel. Aquaman and Aqualad rapidly swim up the channel, boarding the ship just in time. They quickly overpower the alien gangsters, but their leader throws a switch, launching the vessel into orbit. A paralysis beam emitter freezes Aquaman, Aqualad, and Rovere in their tracks. The alien gang leader places each of the three into glass cylinders & launches them into space. At the top of each cylinder is a length of chain, wound around a wheel. Aquaman spins the wheel, releasing the chain from the top of the cylinder. The chain is magnetic and anchors itself to the alien vessel's hull. As Aquaman winds the chain back up, he is drawn up against the ship. Rovere and Aqualad do the same. Aquaman instructs Aqualad to release enough of his chain to lower his capsule over the alien vessel's exhaust port. The aliens begin to succumb to the build up of trapped gasses within their ship. As the alien opens the hatch to clear the obstruction, Aquaman leaps inside. Weakened by the poison fumes, the alien gangsters are easily taken. Rovere pilots the ship back to Earth, returning Aquaman and Aqualad to the surface. Preparing to depart for home, with the captured alien gangsters, Sirene takes a moment to kiss Aquaman goodbye. Mera confides to Aqualad that while she likes Sirene well enough, she's very happy to see her go. Aqualad reassures Mera that Aquaman only has room in his heart for her.