On Outlander, Caitríona Balfe has spent five seasons dubbed “Sassenach,” a Scottish Gaelic word for an English person or outsider — but in BELFAST, she’s anything but one: the Irish actress, 42, portrays a version of writer-director Kenneth Branagh’s mother. Known simply as Ma and seen through the eyes of her 9-year-old son, Buddy (Jude Hill), she is struggling to raise and protect her two children in 1960s Belfast when the nationalist fighting known as the Troubles erupts, plunging their family and way of life into uncertainty.