  We present a deep H-band image of the region in the vicinity of the cluster
Abell 1942 containing the puzzling dark matter concentration detected in an
optical weak lensing study by Erben et al. (2000). We demonstrate that our
limiting magnitude, H=22, would be sufficient to detect clusters of appropriate
mass out to redshifts comparable with the mean redshift of the background
sources. Despite this, our infrared image reveals no obvious overdensity of
sources at the location of the lensing mass peak, nor an excess of sources in
the I-H vs. H colour-magnitude diagram. We use this to further constrain the
luminosity and mass-to-light ratio of the putative dark clump as a function of
its redshift. We find that for spatially-flat cosmologies, background lensing
clusters with reasonable mass-to-light ratios lying in the redshift range 0<z<1
are strongly excluded, leaving open the possibility that the mass concentration
is a new type of truly dark object.
