All-sky CCD observations of short-period mesospheric gravity waves have been made from Halley Station, Antarctica (76¿S, 27¿W). On 27 May, 2001, an unusual wave event exhibiting several features characteristic of a "bore" was observed in the OH, Na, and O2 nightglow emissions. Mesospheric bores are rare wave events that have previously been observed at mid- and low-latitudes. This event was particular interesting as: (1) it initially appeared as a single, high contrast, linear front, accompanied by a sharp enhancement in intensity in all three emissions, (2) a number of trailing wave crests were observed to form with a measured growth rate of 6.6 waves/hr, and (3) the wave pattern exhibited unusual dynamics with significant variability in the observed phase speed and a reduction in the horizontal wavelength by ~50% over a 1-hr period. The location of Halley and the observed propagation suggests a ducted wave consistent with current bore models.