New Zealand, 1932. Two nurses, Louise and Martha, are caring for an invalid patient at his isolated country house in the Wairarapa. The only other occupants are the groundsman and housekeeper.

One evening, the groundsman is forced to drive to town to get a new oxygen cylinder for the patient, who is having breathing difficulties. He won’t be able to return to the house until dawn the next morning.

This causes the women some concern. Over the past few weeks, a killer has been on the loose in the Wairarapa area, and three nurses have been found strangled in their homes.

Conscious of the potential danger, both nurses make sure that all the doors and windows are locked and secure. However, as the night progresses, strange things begin to happen. The housekeeper suddenly becomes incapacitated, objects appear to have been moved without explanation, and bumps and creaks are heard where all should be still.

Are Louise and Martha so on edge that their minds are playing tricks on them? Or could their worse fears be true, and someone else is in the house?