  We report the results of a long-term spectroscopic monitoring of the FS\,CMa
type object MWC\,728. We found that it is a binary system with a B5 Ve (T$_{\rm
eff}$ = 14000$\pm$1000 K) primary and a G8 III type (T$_{\rm eff} \sim$ 5000 K)
secondary. Absorption line positions of the secondary vary with a
semi-amplitude of $\sim$20 km/s and a period of 27.5 days. The system's mass
function is 2.3$\times10^{-2}$ M$_\odot$, and its orbital plane is
$13^{\circ}-15^{\circ}$ tilted from the plane of the sky. The primary's $v \sin
i \sim$110 km/s combined with this tilt implies that it rotates at a nearly
breakup velocity. We detected strong variations of the Balmer and He I
emission-line profiles on timescales from days to years. This points to a
variable stellar wind of the primary in addition to the presence of a
circum-primary gaseous disk. The strength of the absorption-line spectrum along
with the optical and near-IR continuum suggest that the primary contributes
$\sim$60% of the $V$--band flux, the disk contributes $\sim$30%, and the
secondary $\sim$10%. The system parameters, along with the interstellar
extinction, suggest a distance of $\sim$1 kpc, that the secondary does not fill
its Roche lobe, and that the companions' mass ratio is $q \sim$0.5. Overall,
the observed spectral variability and the presence of a strong IR-excess are in
agreement with a model of a close binary system that has undergone a
non-conservative mass-transfer.
