Depleted flux tubes, or plasma bubbles, are one possible explanation of bursty bulk flows, which are transient high speed flows thought to be responsible for a large proportion of flux transport in the magnetotail. Here we report observations of one such plasma bubble, made by the four Cluster spacecraft and Double Star TC-2 around 14:00 UT on 21 September 2005, during a period of southward, but <I>B<sub>Y</sub></I>-dominated IMF. In particular the first direct observations of return flows around the edges of a plasma bubble, and the first observations of plasma bubble features within 8 <I>R<sub>E</sub></I> of the Earth, consistent with MHD simulations (Birn et al., 2004) are presented. The implications of the presence of a strong <I>B<sub>Y</sub></I> in the IMF and magnetotail on the propagation of the plasma bubble and development of the associated current systems in the magnetotail and ionosphere are discussed. It is suggested that a strong <I>B<sub>Y</sub></I> can rotate the field aligned current systems at the edges of the plasma bubble away from its duskward and dawnward flanks.