“Love in Vein” is episode fourteen of season two of Dark Angel.
Max and Original Cindy are at a club when some thugs turn up and start trashing the place. They are much stronger than the average person too, and cause a lot more damage. Later, one turns up in hospital, and she has a barcode on her neck.
Max, naturally enough, assumes that these are fellow Manticore escapees, but when they examine one of them, the barcode is a recent tattoo. They are just human, but they are being given blood by another X5, which they are addicted to and gives them supra-normal abilities.
Joshua does a favour for Alec, and accidentally gets high (not on the X5’s blood though), with less than ideal results – even for drug usage.