A bed covering system is disclosed comprising an upper sheet and a lower sheet wherein the lower sheet fits on a mattress in a removable manner. The upper sheet is connected to the lower sheet through expandable flaps of material. A zipper runs between the sides of the upper and lower sheets such that when it is zipped, the upper sheet is pulled tightly against the lower sheet but when it is unzipped the upper sheet is allowed to move away from the lower sheet to the extent of the expandable flaps or material.