Depends on what you want - the safe route would be 400 speed film, bounced flash and about a 1/20-1/30 shutter speed (a little on the long side to try to bring in some ambient light to the background - but be careful to not show too much motion blur). Another route - depending on how dark - might be 3200 speed black and white film, shot at 3200 with a very fast prime lens like a 50 f1.4. It will still take a steady hand because you'll likely be in the 1/15 range wide open...