A faint \(I_{\rm 170}=4\) MJysr\(^{-1}\) bipolar globule was discovered with the ISOPHOT 170 \(\mu\)m Serendipity Survey (ISOSS). ISOSS J 20246+6541 is a cold (\(T_{\rm d}\approx 14.5\) K) FIR source without an IRAS pointsource counterpart. In the Digitized Sky Survey B band it is seen as a 3\arcmin size bipolar nebulosity with an average excess surface brightness of \(\approx 26\) mag/\(\square \)\arcsec . The CO column density distribution determined by multi-isotopic, multi-level CO measurements with the IRAM-30m telescope agrees well with the optical appearance. An average hydrogen column density of \(\approx 10^{21}\)cm\(^{-2}\) was derived from both the FIR and CO data. Using a kinematic distance estimate of 400 pc the NLTE modelling of the CO, HCO\(^+\), and CS measurements gives a peak density of \(\approx 10^4\)cm\(^{-3}\). The multiwavelength data characterise ISOSS 20246+6541 as a representative of a class of globules which has not been discovered so far due to their small angular size and low 100\(\mu \)m brightness. A significant overabundance of \(^{13}\)CO is found \(X(^{13}CO) \ge 150\times X(C^{18}O)\). This is likely due to isotope selective chemical processes.