Witness (1985). While protecting an Amish boy - who is the sole witness to a brutal murder - and his mother, a detective is forced to seek refuge within their community when his own life is threatened.
This is one of my mum's favourite movies, and I still remember her finally deciding I was old enough to watch it with her (when I probably wasn't, haha) and feeling every way this movie sings. And man, it holds up. Peter Weir really is THAT director, an uncanny touch with both the feminine and the masculine, with tenderness and violence, with languid lyricism and brute, effective punctuation. It's kind of insane to me that his body of work isn't given the same bated-breath treatment as some of his contemporaries. Anyway, this might just be a perfect romantic thriller, and far and away Harrison Ford's best work. 9/10.