Plot Summary: A man is badly injured in a car wreck. Next thing you know there's a carriage bringing a man in a top hat and "Miss Weeks" coming up to an English manor. Pamela, the lady of the house, Anna, meets Christina, the fiance of adopted son Jiles. Mason is the butler, and his sister is unwell. Anna and Hugo, lord of the manor and father of the clan, are getting married. The children seem to take it all right. Next scene, they agree the big meeting went well. Sir Hugo Cunningham photographs something that he is reticent to tell Anna about. He photographs the dead. Anna thinks there's little to learn in photographing the dead. They are getting similar serendipitous smudges on their photographs of the dying. Before a scientific board, it is testified that in one case three different photographers worked hard to get a clean photograph, thus the smudge corresponds to the soul departing at death. This causes quite a stir. The son, Clive, is skeptical. Hugo photographs Christina and her beau on the boat. Clive and Anna are filmed in an old time moving picture in the same fashiony as they canoe across. Clive is struck, sending Anna into the water. She can't swim and she's pulled into the water and both drown. The film is developed and the smudge moves toward him, not away from him. A folk story says one who is about to die knows it. Hugo begins to be obsessed with the question of whether Clive knew he was about to die. A later photograph of Clive shows nothing. The adoptive son thinks this is dangerous. Hugo says that Greek mythology told of the Asphyx. It possesses those about to die and thus is released from unspeakable torment. Jiles thinks this isn't science and that father should stop. He thinks the experiments are pointless and dangerous. He decides he needs a case in which he knows someone is about to die. Edward Barrett gives the good news that they've stepped back into the dark ages: there's to be a public hanging. Barrett says he wants it recorded so that the whole barbarous spectacle can be reported. Hugo begins to see that it's opportune. Amidst protesting placards and anxious onlookers, it's a carnival atmosphere the next day. Jiles is disgusted with his father and leaves the scene. As the execution proceeds, a blue form appears next to the man. Hugo keeps the moving pictures for his own purposes. He seems shaken by it. Hugo refuses to tell Barrett any more. The asphyx apparently stopped in it's movement toward the hanged man. Hugo wonders if the asphyx saw him and that's what made it stop. They also wonder if the blue light from the camera might have spooked it. Hugo thinks it's important that Christina not know about it. Next they check out a guinea pig. The asphyx appears as the guinea pig begins to die, and they coax the asphyx into a container. The claim is that the guinea pig can't die. Next they decide to trap a human asphyx. Christina is becoming very curious about what's going on in the lab. She goes over to the container with the rat's asphyx in it, and she lets the guinea pig go. They arrive at the Bede house. There they see a very sick man. Sir Hugo brings the man with him. Jiles (the adoptee) is Christina's fiance. The man from Bede house has tuberculosis and will die in two days. He specifically asks only to be buried, not dissected. His asphyx hangs over him that night. They trap it in the light and move the box toward the asphyx. The dying man throws acid in sir Hugo's face, and the asphyx comes to him. Hugo strips off the bandage. His search for immortality can't wait. Hugo offers that if he achieves immortality, then the others may have it too. That night, sir Hugo writes a will and tells Jiles to lock the asphyx into an impregnable chamber with a combination lock that will be thrown away once he is immortal. Christina finds the guinea pig whose asphyx was trapped. She puts the guinea pig down and it seeks out its asphyx. Hugo is strapped in and will be slowly electrocuted while Jiles traps his asphyx. The experiment begins and Jiles catches Hugo's asphyx in the blue light. Christina comes in and she helps pull the asphyx into the chamber. They turn off the electrocution device. Later Christina asks Jiles about the experiment. Jiles says he'll tell her if she forgets everything he says. They bring the chamber with Hugo's asphyx to the allotted place. As Jiles begins to unlock it, Hugo awakens. He throws the letter into the fire. Days later, Jiles opens a coffin with sir Hugo in it. Hugo wanted to prove that he couldn't die. He'd been shut in it all night without air and yet survived. Hugo says they're not allowed to marry unless they are immortalized. Barrett happens to be there and Christina talks with him. Hugo is starting to act up. He throws Barrett out with curses. They set up a guillotine. They decide that Christina must be immortalized. The asphyx must sense her fear and that is the best method they could come up with. The apparatus is set up. The blade is held in place and the asphyx appears, but the rat shows up and eats through a vital water vein and the blade cuts her head off. Christina joins the other family members in the vault. Hugo now wants to atone. The new bargain is that Jiles wants to atone forever for what he's done and Hugo wants to die now for the same thing. That's what he says, but Jiles sets it up so that Hugo will kill him too and thus never find the combination that will allow him to get to the asphyx. He burns the combination. This time gassing is the preferred method. A glass casing is dropped over Jiles and the experiment commences. The light booster doesn't work. As the gas goes he lights a match, causing an explosion. Hugo stumbles to his feet alone in his wrecked lab. He stumbles down and thinks about opening the vault but he burns the letter. In the end, we see a corroded looking man stumbling into the accident we saw at the beginning.