'When Calls the Heart': Elizabeth's Family Makes Lucas Feel Uncomfortable (Exclusive)

Lucas Bouchard is meeting his in-laws! In ET's exclusive clip of 'When Calls the Heart,' Lucas is greeted by fiancée Elizabeth Thornton's sister and aunt, but they're not initially warm and welcoming. Watch what happens on the 100th episode of 'WCTH,' which airs Sunday, Aug. 6, at 9 p.m. ET/PT on Hallmark Channel.