A vehicle topper provides an enclosed compartment when coupled with a cargo bed of a vehicle such as a pickup truck. Convenient open access is provided to the bed of the vehicle by employing a rolling door that is supported by a frame within two parallel guide tracks. When the rolling door is in a completely closed position, the vehicle topper creates an enclosed and lockable compartment in conjunction with the cargo bed and the vehicle's cargo box. When the rolling door is moved through the guide tracks to a completely open position, the door is substantially disposed within a sub-floor space between a floor supported by the frame of the vehicle topper, and the vehicle's cargo bed. The rolling door can be caused to bypass the completely closed position and to open in a reverse direction. An outer frame is included to secure the vehicle topper to the walls of the cargo box.