Catching Ianto's movement out of the corner of his eye, Spike eased out of Jack's flesh so he could watch Ianto. Weren't many humans who'd lick blood like that, enjoy the taste of it.
"Wanna be a vampire, Ianto?" he drawled, enjoying the sight as much as Jack was. "Seems like you're halfway there already."
He sank his teeth back into Jack's thigh, a few inches further down, without waiting for an answer.