DR. John Lancaster lives in dread of a family secret from his past being exposed, and makes him act in irrational ways, even with his fiancée Joan Wentworth.

Dr. John Lancaster is a great surgeon, a man of fine instincts, but one who has a hidden second nature. He performs wonderful operations; he does inestimable good for mankind. But sudden periods of temporary atavism come over him and he reverts to primitive type. He sinks into the lowest kinds of vice. He is cruel, heartless, vindictive, unscrupulous. He blasts lives and love without compunction. He is a modern Dr.-Jekyll-and-Mr.-Hyde. As the strange reversion reaches its climax, and death or a madhouse seems the surgeon's inevitable doom, Joan Wentworth, a nurse, enters his life. She is a brave woman who recognizes the victim's genius. Fearlessly she faces all terrifying obstacles to fight his malady. The victory is won; then Lancaster's half-brother appears. It is he who has sought the surgeon's ruin. Seeing his fiendish intent frustrated, the half-brother causes the hospital in which Dr. Lancaster and Joan are asleep to be set afire. As the building burns, he is shot by a maniacal woman. The surgeon escapes, bearing Joan in his arms. That life which the brave little nurse had brought back to him, Dr. Lancaster gives into her keeping.—Moving Picture World synopsis