  Globular clusters in the Milky Way are thought to have either an {\it in
situ} origin, or to have been deposited in the Galaxy by past accretion events,
like the spectacular Sagittarius dwarf galaxy merger. We aim to probe the
origin of the recently discovered globular cluster FSR 1758, often associated
with some past merger event, and which happens to be projected toward the
Galactic bulge, by a detailed study of its Galactic orbit, and to assign it to
the most suitable Galactic component. We employ three different analytical
time-independent potential models to calculate the orbit of the cluster by
using the Gauss Radau spacings integration method. In addition, a
time-dependent bar potential model is added to account for the influence of the
Galactic bar. We run a large suite of simulations to account for the
uncertainties in the initial conditions, in a Montecarlo fashion. We confirm
previous indications that the globular cluster FSR 1758 possesses a retrograde
orbits with high eccentricity. The comparative analysis of the orbital
parameters of star clusters in the Milky Way, in tandem with recent metallicity
estimates, allows us to conclude that FSR1758 is indeed a Galactic bulge
intruder. The cluster can therefore be considered an old metal poor halo
globular cluster formed {\it in situ} and which is passing right now in the
bulge region. Its properties, however, can be roughly accounted for also
assuming that the cluster is part of some stream of extra-Galactic origin. We
conclude that assessing the origin, either Galactic or extra-galactic, of
globular clusters is surely a tantalising task. In any case, by using an {\it
Occam's razor} argument, we tend to prefer an {\it in situ} origin for FSR
1758.
