The Mutant Giant Squids were causing trouble in Jamaica, so H.E.A.T. came to check them out. The squids attacked a ship Elsie Chapman and Mendel Craven are on, appearing all around it. As they almost destroy N.I.G.E.L. and manage to grab Chapman and Craven, covering them in tar. They destroy the ship and take them down underwater.
Afterwards, after N.I.G.E.L. retrieves Chapman and Craven and Nick Tatopoulos gets the tar off of them, the squids attack the ship where the H.E.A.T. team is. After being fended off by the H.E.A.T. crew, Nick gets everyone inside the ship. The Mutant Giant Squids, however, tear away the ship's door and one of them grabs Nick. The squid holds Nick over its mouth, about to eat him. The squid lets him go and all of them submerge, as Zilla Junior appears with one of them in his mouth and spits it away. Zilla holds a couple on his hands and throws them away, but the Mutant Giant Squids all start pulling on Zilla Junior on the same time. Zilla gets dragged underwater briefly, but gets back up again and uses his atomic breath on the squids. Shortly after, the squids' carcasses are found on shore by the H.E.A.T. team, as the Crustaceous Rex appears.
- The Mutant Giant Squids can spit tar that entraps prey and slowly digests them alive.
- The Mutant Giant Squids are adapted to live underwater.
- The Mutant Giant Squids have the strength to hold humans and bring small ships underwater.