  We present an analysis of contemporaneous photospheric, chromospheric and
coronal structures on the highly active K-dwarf star BO Mic (Speedy Mic). We
localize a moderate flare in the stellar atmosphere and study its energetics,
size and thermal behaviour. The analysis is based on strictly simultaneous
X-ray, UV- and optical observations carried out by XMM-Newton and the VLT. We
use Doppler imaging and related methods for the localization of features. Based
on X-ray spectroscopy we study the the coronal plasma in and outside the flare.
The flare emits in X-rays and UV, but is not detected in white light; it is
located at intermediate latitude between an extended spot group and the weakly
spotted pole. We estimate its height below 0.4 stellar radii making it clearly
distinct in longitude and height from the prominences found about two stellar
radii above the surface. While BO Mic's photospheric brightness is modulated
due to extended starspots, neither the chromospheric nor the X-ray emission
show a pronounced rotational modulation.
