ghosts barely exist. They show up only fleetingly, over short distances. In those instants there is a heavy price to be paid, but it isn’t stability or unitarity. Rather, it’s the normally rigid ordering of cause and effect. That minus sign allows ghost particles to briefly skip backward in time, where they can influence particles that they otherwise couldn’t. In this picture, the inexorable forward flow of time that we experience would emerge as a delicate average over lots of temporally squishy micro-moments.