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Streams of gas in cosmological halos are critical to galaxy evolution comma as they bring matter into halos (accretion) and carry matter out (outflows). In addition comma d_commaintergalactic transferd_comma from satellites and group members can be important for building up the gas mass of galaxies. We have discovered a giant (>100 kpc) CORCHETE_OPENO IICORCHETE_CLOSE-emitting nebula in the group environment of a zvirgul0.5 QSO. The filament is devoid of starlight comma showing instead knots of nebular emission in HST-ACS imaging it is coincident in redshift with a partial Lyman-limit system having 1-20 solar metallicity in HST-COS spectroscopy. The filament may be an example of intragroup gas commonly identified via HI-selected absorption studies comma representing either material stripped or shed from group members or accreting with new infall. We propose an ACS-SBC imaging campaign to study the spatial distribution and intensity of O VI and Ly-alpha emission from this filament comma constructing a synthetic narrow band filter through difference imaging in two ACS longpass filters. Our proposed observations will allow us for the first time to understand how the warm-hot and cool phases of circumgalactic gas are related comma provide a robust measure of the cooling rate of hot material in a gaseous halo comma and give unique density and mass estimates in a filament. This filament is one of the few opportunities we have to image intergalactic gas prior to the next generation of UV telescopes and will be the only case for which we have both absorption and emission line data for the same species.