Seagrove starred alongside Rupert Everett in the Academy Award-winning short film A Shocking Accident (1982), directed by James Scott. Her first major film appearance was in Local Hero (1983) in which she played a mysterious Environmentalist with webbed feet. Roles in a number of films including Nate and Hayes (aka, Savage Islands, 1983) opposite Tommy Lee Jones and Appointment with Death (1988) followed. One of her lead starring roles was in The Guardian (1990), directed by william Friedkin, in which she played an evil babysitter. In 2017, she played the lead role in Another Mother's Son, starring as Louisa Gould, a member of the Channel Islands resistance movement during World War II, who famously sheltered an escaped Russian slave worker in Jersey. She was later gassed to death in 1945 at Ravensbrück concentration camp.