In the late 19th century, Sir Ronald Burton and Countess Elga Von Bruno lie in coffins, alive but immobile.  As Ronald attempts through his thoughts to convince a servant, Fender, that he is not really dead, he remembers how he came to this situation: In Vienna, a friend from the British embassy secures for Ronald an invitation to the home of cruel Count Karl Von Bruno.

Years earlier, Ronald had traveled to Africa with his friends, Sterling and Brown, to establish an ivory empire for England.  Once there, they discovered Von Bruno attempting to take control of a local tribe and its riches by posing as a God.  When the Englishmen attacked and wounded Von Bruno, however, the natives realized that he was not immortal and chased him out.  Sterling and Brown have since disappeared, and Ronald believes that Von Bruno killed them.

Traveling to the Count's castle under the name Richard Beckett, Ronald and his servant, Romley, soon find proof of Von Bruno's treachery when they stop at the Green Man Inn.  Ronald mentions Sterling and Brown, and the proprietor, obviously lying, states that he has never met them.  The Englishman then invites Von Bruno's driver, Fender, to dine with him, and the inappropriateness of this request prompts Von Bruno's cohorts, Steiken and Ernest Von Melcher, to challenge him to a duel, which Ronald wins easily.

The next day, Ronald arrives at the castle and, as he begins a clandestine search, meets the Count's beautiful, innocent wife Elga.  Ronald and Elga accompany Von Bruno to view the African leopard he has imported for the next day's hunt, and Elga cringes as Von Bruno beats the starving cat.  On the way back to her room, a trap door closes behind them, imprisoning them on a ledge over a pit of alligators.  Von Bruno, though now suspicious of Ronald, rescues them.  At the hunt the next day, the Count, who has placed the leopard in a pit, tricks Ronald into tumbling down the incline.  As Ronald bravely wrestles the leopard, Von Bruno shoots it.

During a celebration that night, Von Bruno presents Ronald with a gift of pistols as he flirts with a lovely aristocrat.  When Ronald dances with Elga, he notices that her necklace, a gift from the Count, bears the insignia given to him and his friends while they were in Africa.  At her door, Ronald then steals the necklace as he kisses her.  Minutes later, however, he returns it and confesses his love.  Von Bruno's physician, Dr. Meissen, listens as Ronald reveals that the African natives gave Ronald, Sterling and Brown the matching insignias as thanks for saving them from Von Bruno.  After Elga agrees that he must take the pendant to the German emperor as proof that Von Bruno killed Sterling and Brown, Ronald swears to return for her.  Steicken has also overheard Ronald's confession, but Dr. Meissen poisons him before he can warn Von Bruno.  The Count then confronts Elga, who informs him that she loves only Ronald.  The next morning, Ronald leaves the castle with the pendant, but is stopped by Dr. Meissen, who, after addressing him as "Sir Ronald," convinces him that Von Bruno is planning to kill Elga.

Meanwhile, Von Bruno learns from the inn's proprietor that Ronald asked after Sterling and Brown, and realizes that "Richard Beckett" is actually his old foe.  When Ronald returns to the castle, Von Bruno throws him into a dungeon cell with Elga, vowing to torture them to death.  That night, Romley sneaks into the cell and frees the lovers.  Although Romley sacrifices his life to protect them, they are caught and imprisoned again by Von Bruno.  Dr. Meissen then presents a drug which will make them appear to be dead for ten hours, after which they will revive and be able to escape from the mausoleum in which Von Bruno will inter them.

When Von Bruno finds them apparently dead, however, he threatens Dr. Meissen until he reveals the truth, after which the Count prepares to bury the lovers alive.  In the present, Von Bruno kills Dr. Meissen as he secretly drops Ronald's pistols into the coffin.  Fender then nails the coffin lid on, but pries it open again when he hears Ronald knock.  Just as Von Bruno appears, Ronald jumps out of the coffin and shoots him.  Ronald then takes the reviving Elga into his arms and asks Fender to remain with him as his servant.