Carys is placed in a holding cell in Torchwood's hub. As tests are run on Carys, Gwen feels uncontrollable urges to kiss her, showing that Carys is emitting high levels of pheromones, effectively becoming a "walking aphrodisiac", but the gas is also slowly killing her.
Carys is held captive at Torchwood headquarters for testing, and Gwen experiences intense urges to kiss her due to the high levels of pheromones emitted by her, making her a potent aphrodisiac. The gas slowly killing Carys.