  We present new multiband CCD photometry for WZ Cyg made on 22 nights in two
observing seasons of 2007 and 2008. Our light-curve synthesis indicates that
the system is in poor thermal contact with a fill-out factor of 4.8% and a
temperature difference of 1447 K. Including our 40 timing measurements, a total
of 371 times of minimum light spanning more than 112 yr were used for a period
study. Detailed analysis of the $O$--$C$ diagram showed that the orbital period
has varied by a combination with an upward parabola and a sinusoid. The upward
parabola means the continuous period increase and indicates that some stellar
masses are thermally transferred from the less to the more massive primary star
at a rate of about 5.80$\times10^{-8}$ M$_\odot$ yr$^{-1}$. The sinusoidal
variation with a period of 47.9 yr and a semi-amplitude of 0.008 d can be
interpreted most likely as the light-travel-time effect due to the existence of
a low-mass M-type tertiary companion with a projected mass of $M_3 \sin
i_3$=0.26 M$_\odot$. We examined the evolutionary status of WZ Cyg from the
absolute dimensions of the eclipsing pair. It belongs to the marginal contact
binary systems before broken-contact phase, consisting of a massive primary
star with spectral type of F4 and a secondary with the type K1.
