Silent intruder

"Michael and Hilda return from vacation to find the police waiting for them with a tip that child pornography is being stored on Michael's computer, but after he is proven innocent they realize that someone has been staying in their house."@en
"When Michael McGinnis and Hilda Gilmour return from holiday to find two plainclothes police officers waiting for them outside their secluded East Lothian cottage it marks the start of a terrifying journey. The police have had an anonymous tip-off about child pornography being stored on Michael's computer. It's easy to prove his innocence but who would do such a thing and why? At the same time it becomes clear that someone was living in the cottage while they were away, and may still be returning when they are both out. As the couple try to find some answers and uncover the identity of the mysterious intruder they soon get sucked into a world of violence and organized crime. The police warn them not to get involved, but when they no longer feel safe in their own home they decide to take action, with devastating consequences ..."