The investigators are in the thick of combat. Charles Johnson, the insane attendant, narrowly misses Chet with his wood axe but manages to deliver a near fatal blow to Eileen and a terrible wound to the Doc before finally being put down by the reporter. The group have to administer emergency first aid to half their number before rushing back to the sanatorium to perform life saving surgery on Eileen.
While Eileen is undergoing emergency treatment Chet wanders downstairs to the basement at the sound of frantic screaming and witnesses the manic street preacher, Leonard Hawkins, being plucked out from his cell by a gaseous semi-solid tentacle. Chet manages to save Darlene from a similar fate by successfully warding the creature off with the Elder sign pendant he took from Eileen. Depositing Darlene with the others up in the treatment room Chet returns to the basement to rescue the remaining two special patients. Allen Harding however, has been possessed by the cosmic creature and issues dire mocking threats prior to exploding in a mist of bone and gristle before Chet’s very eyes; the reporter only comes to his senses again when the Prof joins him and Blanche begins to scream from her cell. Armed with two Elder sign sigils the duo manage to save the deranged old lady from the multi-coloured alien.
Rushing upstairs they are able to see the full dimensions of their adversary – it is a gaseous multi-coloured creature half the size of the building. The group struggle to decide what to do next, and Chet unsuccessfully attempts to cast a spell to contact his serpentine benefactor. Amid the indecision the group soon find themselves under further assaults from their foe; it possesses Blanche and nearly succeeds in dragging the Prof over to the window to be consumed by the waiting creature and he is only just saved by a lucky blow (although he is shot in the process by the good Doc!); the Prof then angrily turfs the elderly patient out of the window to be absorbed by the monster. Wisely retreating into the corridor the group briefly experiment with Molotov cocktails and contemplate dousing the creature with tap water (which would have been futile as it is only susceptible to salt water!) when it is Darlene’s turn to be possessed and she makes an attempt to feed herself to the creature by diving out of the window; which she is prevented from doing.
After further debate it is finally settled that Chet is the only member of the team who is physically capable of escaping the monster. A plan is formulated to lead it to the docks where they hope to then drive it into the waters with the Elder sign sigils, but they correctly theorise that more signs are required and incorrectly, that another can probably be found on Johnson’s body which they had neglected to search. Chet heads out of the building via the back door and makes it to the corner of the woods before observing that he is being pursued. After an epic battle of wills Chet manages to search the body and finds nothing of use before succumbing to the alien creature’s powerful mind control which forces him to drop his protection and allow himself to be consumed. Finally the alien entity has absorbed the required amount of life force to permit it to ascend from the earthly realm and enter another dimension as an even more powerful being.
The terrible transformation turns night into day and rends the very earth with fissures. The ground begins to shake terribly and the sanatorium begins to collapse in on itself. The Doc, giving in to his own sense of self-preservation, abandons his patient and compatriots and manages to jump from the top floor of the building and scale a tree with impressive monkey-like skills, before racing down towards the dock where safety awaits, but ultimately to no avail – his extremely weekend condition means that he does not survive a heat blast and therefore tragically falls at the last hurdle. The Prof manages to maintain his cool under pressure and heroically attempts to save the lives of the others. He unwisely chooses to push Eileen’s trolley down the top flight of stairs and the gravely wounded and fragile Eileen dies as a result of the tumble. The Prof then rushes back into the corridor to rescue Darlene but his time has run out and the entire building collapses and buries them both. Fortunately for the both of them they are not conscious when the creature completes its transformation and ascension, which blasts the island with an explosive force that bakes and burns everything.
Everyone is dead. The other-worldly culprit has truly left the scene. When the authorities do visit the island the next day they are greeted only with a scene of utter devastation and a unsolvable mystery. The most plausible of the subsequent theories is that one or more of the patients escaped from their cells, ran amok and murdered everyone before setting fire to all the buildings on the island……