Jack cried out helpless in his pleasure every part of him screaming "Yes god yes at last." His mate was where he belonged and as such Jack's inner walls began to shift and change taking Ianto deeper to hit the one place inside the older man that would change their lives forever.
It would take another few rounds for Jack's chemical signature to change as he had gone too long without satisfying his need. But for now Jack screamed and spilled his seed against the door as he shoved his hips back against Ianto's cock.