  Infrared-Faint Radio Sources represent a new and unexpected class of object
which is bright at radio wavelengths but unusually faint at infrared
wavelengths. If, like most mJy radio sources, they were either conventional
active or star-forming galaxies in the local Universe, we would expect them to
be detectable at infrared wavelengths, and so their non-detection by the
Spitzer Space Telescope is surprising. Here we report the detection of one of
these sources using Very Long Baseline Interferometry, from which we conclude
that the sources are driven by Active Galactic Nuclei. We suggest that these
sources are either normal radio-loud quasars at high redshift or abnormally
obscured radio galaxies.
