  We aim to understand the multi-wavelength properties of 2XMM J123204+215255,
the source with the most extreme X-ray-to-optical flux ratio amongst a sample
of bright X-ray selected EXOs drawn from a cross-correlation of the 2XMMp
catalogue with the SDSS-DR5 catalogue. We use 2XMMp X-ray data, SDSS-DR5, NOT
and UKIRT optical/NIR photometric data and Subaru MOIRCS IR spectroscopy to
study the properties of 2XMM J123204+215255. We created a model SED including
an obscured QSO and the host galaxy component to constrain the optical/IR
extinction and the relative contribution of the AGN and the galaxy to the total
emission. 2XMM J123204+215255 is a bright X-ray source with f_X~10^{-12} erg
cm^{-2} s^{-1} (2-10 keV energy band) which has no detection down to a
magnitude i' > 25.2. NIR imaging reveals a faint K-band counterpart and NIR
spectroscopy shows a single broad (FWHM=5300 km/s) emission line, which is
almost certainly H-alpha at z=1.87. The X-ray spectrum shows evidence of
significant absorption (N_H > 10^{23} cm^{-2}), typical of type 2 AGN, but the
broad H-alpha emission suggests a type 1 AGN classification. The very red
optical/NIR colours (i'-K > 5.3) strongly suggest significant reddening
however. We find that simple modelling can successfully reproduce the NIR
continuum and strongly constrain the intrinsic nuclear optical/IR extinction to
A_V~4, which turns out to be much smaller than the expected from the X-ray
absorption (assuming Galactic gas-to-dust ratio).
