When Valdemar returned a victor from Esthonia, having beaten alike the pagans and the Livonian knights, and bearing with him the victorious Danneborg, he was at the height of his glory, and none dreamed of the terrible disaster that awaited him. He had made enemies among the German princes, and they conspired against him, but they were forced to submit to his rule. Some of those whose lands he had seized did not hesitate to express openly their hatred for him; but others, while secretly plotting against him, pretended to be his friends, shared in his wars and his courtly ceremonies, and were glad to accept favors from his hands.
One of those who hated him most bitterly, yet who seemed most attached to him, was the Count-Duke of Schwerin, a man who, alike from his dark complexion and his evil disposition, was known in his own country as "Black Henry." The king had often been warned to beware of this man, but, frank and open by nature and slow to suspect guile, he disregarded these warnings and went on treating him as a trusty friend.
This enabled Count Henry to make himself familiar with Valdemar's habits and mode of life. He secretly aided certain traitors who cherished evil designs against the king; but when he found that all these plots failed he devised one of his own which the king's trust in him aided him in carrying out.
In the spring of the year 1233 Valdemar invited his seeming friend to a two days' hunt which he proposed to enjoy in the woods of Lyö, but the count sent word that he regretted his inability to join him, as he had been hurt by a fall and could not leave his bed.
His bed just then was his horse's saddle. The opportunity which he awaited had come, and he spent the night scouring the country in search of aid for the plot he had in view, which was no less than to seize and hold prisoner his trusting royal friend. He knew the island well, and when his spies told him that the king and his son Valdemar had landed at Lyö with a small following of huntsmen and servants, Black Henry prepared to carry out his plot.
The king's first day's hunt was a hard one and he and his son slept soundly that night in the rude hut that had been put up for their use. No one thought of any need of guarding it and the few attendants of the king were scattered about, sleeping under the shelter of rocks and trees.
Late that night Count Henry and his men landed and made their way silently and cautiously through the tired sleepers to the royal hut, which he well knew where to find. Quietly entering, they deftly gagged the king and prince before they could awake, and before either of them could raise a hand in resistance sacks of wool and straw were drawn over their heads, so closely as nearly to choke them, and strong bonds were tied round their legs and arms.
Thus thoroughly disabled, the strong king and his youthful son were carried through the midst of their own people to the strand and laid helplessly in the bottom of the waiting boat, which was rowed away with muffled oars, gliding across the narrow sound to the shore of Fyen. Here waited a fast-sailing yacht to which the captives were transferred, sail being set before a favoring wind for the German coast.
The next morning, when the king's attendants were searching for the missing king, he and his son, still bound and gagged, were landed on a lonely part of the sea-shore, placed on awaiting horses, and tightly secured to the saddles, after which they were hurried on at full gallop, stopping only at intervals to change the armed escort, until the castle of Danneberg, in Hanover, was reached.
This castle had been loaned by its owner to Count Henry, he having no stronghold of his own deemed secure enough to hold such important captives. So roughly had they been treated that when the bonds were removed from Prince Valdemar, who resembled his mother Dagmar alike in his beauty and her feebleness, the blood flowed from every part of his body. Yet, without regard to his youth and sufferings, the cruel captor shut up him and his royal father in a cold and dark dungeon, where they were left without a change of clothing and fed on the poorest and coarsest food.