The Crucial Test (1916)

Wicked Russian Grand Duke Bagroff becomes infatuated with Thanya, but she loves American artist Vance Holden. When Thanya's revolutionary brother Boris tells her that he plans to kill Bagroff, she agrees to help. The plan fails and Boris and Thanya are captured, but they soon escape to Paris where Thanya rejoins the struggling Vance. Bagroff finds Thanya and tells her that he will make Vance famous if she consents to be his mistress. Thanya agrees and Vance becomes an overnight success. Then, as Bagroff and Thanya prepare to spend their first night together, Boris appears and kills the duke, thereby allowing Thanya and Vance to spend a peaceful, successful life together.