Adapted from William J. Makin's novel, a reporter and doctor discover that a criminal doctor is murdering to get blood to keep alive.
Reporter Walter Garrett (Wayne Morris) calls Angela Merrova (Lya Lys) for an interview; but he finds her dead. When police detective Roy Kincaid (Charles C. Wilson) arrives, the body is gone. Walter's editor (Joseph Crehan) shows him Angela and fires him. Walter goes to Dr. Michael Rhodes (Dennis Morgan) and says Angela had a deep stab wound in her chest but looked clammy. Rhodes needs rare blood, but Rogers does not arrive. Nurse Joan Vance (Rosemary Lane) volunteers. Dr. Francis Flegg (John Litel) does the transfusion. Police call Rhodes, and Kincaid shows Walter and him Rogers dead without blood in his body. Kincaid says the coroner reported Rogers was operated on, but Rhodes says his blood was a different group than the stains. Rhodes tells Walter it is neither human nor animal blood. Walter follows Rhodes, who calls on Flegg. Marshall Quesne (Humphrey Bogart) tells Rhodes he is interested in blood. Rhodes asks Flegg to examine the blood. Rhodes asks Flegg if Quesne is anemic and if the blood is artificial, as Quesne cuts himself. Flegg says it is blood group 4. After Rhodes leaves, Angela comes in and faints. From the window Walter sees Flegg treat her.
Walter tells Rhodes his suspicions. Flegg asks Rhodes for Joan's address. Rhodes has a date with Joan, but he and Walter call on Angela, who faints. She admits she was attacked and woke up in her room. Quesne comes in. Walter and Rhodes go to the house of Walter's editor to say that Angela was stabbed. He calls the paper and learns that Angela is dead. Walter and Rhodes go to see Angela's body. Walter learns from news clippings that Quesne was Dr. Xavier, who was convicted of murder and electrocuted. Walter and Rhodes go to Xavier's grave and find his coffin empty. Flegg admits to them that Quesne is Xavier revived after death. Flegg shows them a dead rabbit and revives it. Flegg says that Quesne is a medical genius, but Flegg's synthetic blood does not last; so Angela died. Quesne kills to get blood to stay alive. Outside Kincaid arrests Walter and Rhodes for snatching a body. Quesne shoots Flegg to get a list of blood donors. Flegg tells Rhodes that Quesne got the list. Quesne tells Joan he will take her to Flegg but abducts her to a country house. Walter tells Kincaid where. Joan screams. In the shoot-out Quesne is killed. Walter writes the sensational articles. In the final scene a new secretary induces Walter to sign a contract with his editor.
This drama explores a horrific result of experimenting
with artificial blood with an executed murderer, reflecting some
of the bizarre possibilities opened up by recent medical discoveries
such as blood groups.