Her American Prince (1916)

A young American doctor and his brother are involved in an auto accident in a foreign country. The doctor happens to catch a glance of a beautiful princess and falls immediately in love. Meanwhile, in a neighboring country, the princess' husband--a spoiled wastrel who happens to look just like the doctor--is in pursuit of a courtesan. The doctor overhears a group of army officers plotting to kill the king and put the prince on the throne. Unfortunately for the doctor, the plotters mistake him for the prince.