  The quasar HE0450-2958 was recently discovered to reside ~7kpc away from a
galaxy that was likely disturbed by a recent merger. The lack of a massive
spheroid of stars around the quasar raised the unlikely suggestion that it may
have formed in a dark galaxy. Here we explain this discovery as a natural
consequence of a dynamical kick imparted to the quasar as it interacted with a
binary black hole system during a galaxy merger event. The typical stalling
radius for a ~10^9 solar mass binary provides a kick of order the escape
velocity of the stellar spheroid, bringing the quasar out to around the
observed radius before it turns around. This is consistent with the observed
low relative velocity between the quasar and the merger-remnant galaxy. The gas
carried with the black hole throughout the three-body interaction fuels the
quasar for the duration of its journey, ~2x10^7 years. Gravitational radiation
recoil could not have produced the required kick.
