Susannah Mackay is an engaging actress known for her standout role in the cult holiday horror film "Once Upon a Time at Christmas" (2017). This unique blend of festive cheer and slasher thrills has garnered a dedicated following, making it a sought-after title among collectors of niche horror and Christmas-themed movies. Mackay's performance lends a captivating energy to the film, which has been praised for its inventive storyline and engaging characters. Collectors are particularly drawn to the physical media releases of "Once Upon a Time at Christmas," with its limited edition Blu-rays and exclusive behind-the-scenes content providing a treasure trove of insights into the filmmaking process. Mackay's involvement not only elevates the film but also solidifies her status as a key figure in contemporary genre cinema, making her work a must-have for any serious collector looking to explore the intersection of holiday cheer and horror.