Star Trek: The Next Generation - Birthright

While the Enterprise is docked at Deep Space Nine, providing assistance in repairing the Bajoran aqueducts, Worf is approached by an Yridian information broker, Jaglom Shrek, who claims that Worf's father was not killed at Khitomer, but is instead alive at a Romulan prison camp. Since Mogh's capture would dishonor Worf and his own son, Worf is reluctant to believe the alien's claim but it upsets him. However, following an accident, Data has a dream-like experience that involves his creator and Data approaches Worf to ask about a time Worf himself had a hallucination during a Klingon ritual. Worf realizes that it is important to learn the truth about his father.