Glam was not prepared for this, being then in the act of pulling Grettir towards him, so he fell backwards and went crashing out through the door, his shoulders catching the lintel as he fell.

The roof of the porch was wrenched in two, both rafters and frozen thatch, and backwards out of the house went Glam, with Grettir above him.
"Outside there was bright moonshine and broken clouds, which sometimes drifted over the moon and sometimes left it clear.

At the moment when Glam fell the cloud passed off the moon, and he cast up his eyes sharply towards it; and Grettir himself said that this was the only sight he ever saw that terrified him.

Then Grettir grew so helpless, both by reason of his weariness and at seeing Glam roll his eyes so horribly, that he was unable to draw his dagger, and lay well-nigh between life and death.
"But in this was Glam's might more fiendish than that of most other ghosts, that he spoke in this fashion: 'Great eagerness have you shown to meet me, Grettir, and little wonder will it be though you get no great good fortune from me; but this I may tell you, that you have now received only half of the strength and vigour that was destined for you if you had not met with me.

I cannot now take from you the strength you have already gained, but this I can see to, that you will never be stronger than you are now, and yet you are strong enough, as many a man shall feel.