Robert Thatcher invents a device to protect banks from thieves. This is bought up for a few thousands by Thomas who later makes a million out of Thatcher’s invention. Thatcher, discovering a weakness in his system, perfects this, and when he offers the perfect invention to Thomas for $50,000, his offer is refused and he is ordered out of the office. This breaks his heart and he dies in poverty. His young son, Robert, about to finish his course at an institute of technology, discovers the truth about the Thomas patent and how his father was cheated. He gets work in the Thomas shops and deliberately sets about to prove the weakness of the “Safe Protective” system. When he has gained all the knowledge he needs he sets out to break every bank carrying the Thomas system. His little sweetheart, Madge, afraid to let him go alone, accompanies him, attired in boy’s suit and cap. The Thomas people receive reports from all their protected banks, telling of a mysterious cracksman, who, with master hand, opens every safe, proving that the Thomas System has a flaw. But strange to relate, the bank breaker steals not a cent. A detective is put on the case and one night he apprehends Robert and his little “pal” in the act of breaking into the Shoe and Leather Bank. The girl breaks down and Robert tells their story to the detective whose sympathy is awakened. He goes to Thomas and tells him that unless Robert is given $50,000 and a share in the business created by his father’s invention, he will spread the story broadcast through the medium of the press. Thomas is forced to agree to this demand and Robert comes into his own at last.