A Dark Lantern

A Dark Lantern is a lost 1920 American silent drama film produced and released by Realart Pictures. It is based on a 1905 novel of the same name by Elizabeth Robins.
John S. Robertson directed and Alice Brady and her then husband James Crane star.
According to the AFI Catalog, the film was shot at the Essanay studios in Chicago as that was where Alice Brady was appearing in a play at the time.
Plot.
As described in a film magazine, mistaking the intentions of Prince Anton (Denny) of Argovinia in seeking her hand, young English woman Katherine Dereham (Brady) suffers a great shock when his attentions culminate in a proposal that she be his morganatic wife, his country requiring an alliance with a royal princess. This, together with the blow of her father's death, shatters Katherine's nerves and causes a breakdown. She recovers under the rigid administrations of Dr. Garth Vincent (Crane). Her attitude of antagonistic exaggeration of his sternness that conceives it as sheer brutality makes her submission to the deep love he bears her a sorrowful task. His patience at last breaks her embittered spirit and sends her to his home, willing to accept his protection under compromising circumstances. The realness of his affection is at last revealed to her and Prince Anton, whose love for Katherine has made him risk his throne by divorcing his wife, is sent back to Argovinia.