His head struck the doorpost with a great thud, and there he lay motionless, while something flew from his hand across the floor, rattling as it went.

It was the hilt of a knife of some sort.
Erling shut the outer door in haste, and then helped me to rise, asking me if I were hurt.
"No," I answered.

"Ho, but what is that ?" Out of my tunic as I straightened myself there fell a gleaming blade, and I picked it up.

It was half of a Welsh knife, keen and pointed, which had broken on my mail shirt, leaving only a long slit in my tunic, and maybe a black bruise to come presently on the skin where the dint fell.
"I owe life to you, Erling," I said.

"And I laughed at the thought of wearing the mail, and well-nigh did not put it on.