We present very deep WFPC2 images and FOS spectroscopy from the Hubble Space Telescope ( HST ) together with numerous supporting ground–based observations of the field of the quasar 3C 336 ( z _ { em } = 0.927 ) .
The observations are designed to investigate the nature of galaxies producing metal line absorption systems in the spectrum of the QSO .
Along a single line of sight , we find at least 6 metal line absorption systems ( of which 3 are newly discovered ) ranging in redshift from 0.317 to 0.892 .
Through an extensive program of optical and IR imaging , QSO spectroscopy , and faint galaxy spectroscopy , we have identified 5 of the 6 metal line absorption systems with luminous ( L _ { K } \geq 0.1 L _ { K } ^ { \ast } ) galaxies .
These have morphologies ranging from very late–type spiral to S0 , and exhibit a wide range of inclination and position angles with respect to the QSO sightline .
The only unidentified absorber , despite our intensive search , is a damped Lyman \alpha system at z _ { abs } = 0.656 .
Analysis of the absorption spectrum suggests that the metal abundances ( [ Fe/H ] = -1.2 ) in this system are similar to those in damped systems at z \sim 2 , and to the two other damped systems for which abundances have been determined at z < 1 .
The absorption line system must either be associated with an underluminous , late–type spiral galaxy which we find at a projected disk impact parameter of \sim 120 h ^ { -1 } kpc , or with an as yet unseen , extremely faint galaxy ( L < 0.05 L _ { K } ^ { \ast } ) near the QSO sightline that eludes detection despite our deep HST and high resolution ground based near–IR images .
We have found no examples of intrinsically faint galaxies ( L < 0.1 L ^ { \ast } ) at small impact parameters that might have been missed as absorber candidates in our previous ground–based imaging and spectroscopic programs on MgII absorbing galaxies .
We have , however , identified several intrinsically faint galaxies within \sim 50 h ^ { -1 } kpc of the QSO sightline which do not produce detectable metal line absorption .
There are no bright galaxies ( L > 0.1 L _ { K } ) within 50 h ^ { -1 } kpc which do not produce detectable metal lines ( of Mg II \lambda \lambda 2796 , 2803 and/or C IV \lambda \lambda 1548 , 1550 ) in the QSO spectrum .
All of these results generally support the inferences which we have previously reached from a larger survey for absorption–selected galaxies at z \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 1 .

There are several other galaxies with redshifts near that of 3C 336 , suggesting that the QSO is situated in an overdense region , perhaps a galaxy cluster .
Previously published reports of a cluster around 3C 336 were largely misled by the presence of many foreground galaxies seen in projection near the QSO .
It is possible that a reported measurement of weak shear gravitational lensing in this field may be produced by the QSO cluster itself , as there appear to be no other groups or clusters in the foreground .
We find no evidence for a normal , bright QSO host galaxy , although there are several faint objects very close to the quasar and at similar redshift which might either be companions or part of a disorganized QSO host .