1 Introduction

Bok globules were originally detected in absorption against HII regions by Bok & Reilly (1947), and are known as small, dense interstellar clouds in the solar neighbourhod ( $d\lessapprox 400$ pc). They were identified optically, and mostly the nearby ones have been catalogued so far. It is expected that they are similarily common elsewhere in the Galactic disk and in fact a few distant ones have already been investigated e.g. by Launhardt & Henning (1997). Their FIR properties were determined by Clemens & Barvainis (1988) based on IRAS data. They emphasized the importance of finding FIR faint cold globules since these are representatives of the inactive (i.e. non-starforming) interstellar medium. Starless globules with small apparent size and low temperature (thus also very low 100 $\mu$m brightness) can be seen only by good sensitivity at wavelengths over 100 $\mu$m. An ISOPHOT study of pre-stellar cores in dark clouds with low 100 $\mu$m brightness was recently reported by Ward-Thompson et al. (2002). The ISOPHOT 170 $\mu$m Serendipity Survey (ISOSS) (Bogun et al. 1996) can be used to locate cold galactic objects even without any preliminary identification. This raises the possibility of detection of the "missing'' globules via ISOSS. Our preceeding papers on ISOSS observations of interstellar clouds discussed cold cores in the well known Chamaeleon cloud complex (Tóth et al. 2000) and in the known B 68 globule (Hotzel 2001). We present our results on ISOSS J20246+6540 proving that it is, a small and cold isolated molecular cloud - one of the so far missed population.