  We show that a string of HI clouds that form part of the high-velocity cloud
complex known as GCN is a probable gaseous stream extending over more than 50
deg in the Galactic halo. The radial velocity gradient along the stream is used
to deduce transverse velocities as a function of distance, enabling a family of
orbits to be computed. We find that a direction of motion towards the Galactic
disk coupled with a mid-stream distance of ~20 kpc provides a good match to the
observed sky positions and radial velocities of the HI clouds comprising the
stream. With an estimated mass of 10^5 Msun, its progenitor is likely to be a
dwarf galaxy. However, no stellar counterpart has been found amongst the
currently known Galactic dwarf spheroidal galaxies or stellar streams and the
exact origin of the stream is therefore currently unknown.
