A linear pretensioner for use as part of a motor vehicle occupant belt restraint system mountable to vehicle structure and coupled with a belt restraint system component. The pretensioner includes at least one base plate having a slot and at least one closure plate fixedly attached to the base plate. The closure plate(s) and the slot of the base plate(s) form a cavity having an open end. A piston plate has a piston tail slidably disposed within the cavity and a piston head extending from the open end. A cable is coupled with the piston plate, the base plate(s), and/or the closure plate(s). The piston plate, the slot of the base plate(s), and the closure plate(s) cooperate to form an expanding chamber that enlarges when pressurized by a gas generator, which drives the piston plate and the base plate relative to each other to exert tension on the cable.