When struggling writer Sebastian finds a room to let in a palatial Hampstead residence he cannot believe his luck. The rent is ridiculously cheap and he immediately feels a connection with his beautiful widowed landlady, Adriana. Things take a dark turn when he finds out what happened to the last lodger. Could this be why the house is a fortress of security, and why Adriana seems so fragile? Adriana doesn't want to talk about the death and sadness that seem to follow her wherever she goes and Sebastian has secrets of his own. Now someone is watching their every move and there is nowhere to hide. This house of light becomes a dark nightmare as the threat ramps up - what does the watcher want? And how far will they go to get it?