There was another castle before which Harald had come with his army. This castle was both full of people and so strong, that there was no hope of breaking into it. The castle stood upon a flat hard plain. Then Harald undertook to dig a passage from a place where a stream ran in a bed so deep that it could not be seen from the castle.
They threw out all the earth into the stream, to be carried away by the water. At this work they laboured day and night, and relieved each other in gangs; while the rest of the army went the whole day against the castle, where the castle people shot through their loop-holes.
They shot at each other all day in this way, and at night they slept on both sides. Now when Harald perceived that his underground passage was so long that it must be within the castle walls, he ordered his people to arm themselves. It was towards daybreak that they went into the passage. When they got to the end of it they dug over their heads until they came upon stones laid in lime which was the floor of a stone hall.
They broke open the floor and rose into the hall. There sat many of the castle-men eating and drinking, and not in the least expecting such uninvited wolves; for the Varings instantly attacked them sword in hand, and killed some, and those who could get away fled. The Varings pursued them; and some seized the castle gate, and opened it, so that the whole body of the army got in.
The people of the castle fled; but many asked quarter from the troops, which was granted to all who surrendered. In this way Harald got possession of the place, and found an immense booty in it.