terrance quinn (born july 15, 1952), known professionally as terry o'quinn, is an american actor. he is best known for portraying the role of john locke in the abc drama mystery series "lost", which ran for six seasons (2004–2010). he also played the title role in "the stepfather" and "stepfather ii", and played peter watts in the crime drama series "millennium", which ran for three seasons (1996–1999).