He waits, until Jack starts to turn back toward the fire.

Now.

One hand wrapped in cloth from his shredded jeans, the other holding the knife. Oliver bursts out from under the blanket, scooping ash and embers in his protected hand and hurling them into Jack's face.

Then he's over the fire - scattered, hissing in patches of snow where it doesn't burn against the shelter's floor - and on top of the spirit, knife against where a human's carotid would be. Jack may not have bled much the last time Oliver cut him, but he still bled.

Do it.

He grits his teeth, heartbeat gagging him. One chance. Right here.

Do it.