It had been kept for some weeks past in the prisoner’s study.  His wife thought—­although it was two finger breadths less than four feet in length, and not very broad or deep in proportion—­that it might be possible for him to get into it.  He was considerably above middle height, but found that by curling himself up very closely he could just manage to lie in it with the cover closed.  Very secretly they had many times rehearsed the scheme which had now taken possession of their minds, but had not breathed a word of it to any one.  He had lain in the chest with the lid fastened, and with his wife sitting upon the top of it, two hours at a time by the hour-glass.  They had decided at last that the plan, though fraught with danger, was not absolutely impossible, and they were only waiting now for a favourable opportunity.  The chance remark of the child Cornelia settled the time for hazarding the adventure.  By a strange coincidence, too, the commandant of the fortress, Lieutenant Deventer, had just been promoted to a captaincy, and was to go to Heusden to receive his company.  He left the castle for a brief absence that very Sunday evening.  As a precautionary measure, the trunk filled with books had been sent to Gorcum and returned after the usual interval only a few days before.

The maid-servant of the de Groots, a young girl of twenty, Elsje van Houwening by name, quick, intelligent, devoted, and courageous, was now taken into their confidence.  The scheme was explained to her, and she was asked if she were willing to take the chest under her charge with her master in it, instead of the usual freight of books, and accompany it to Gorcum.

She naturally asked what punishment could be inflicted upon her in case the plot were discovered.

“None legally,” answered her master; “but I too am innocent of any crime, and you see to what sufferings I have been condemned.”

“Whatever come of it,” said Elsje stoutly; “I will take the risk and accompany my master.”

Every detail was then secretly arranged, and it was provided beforehand, as well as possible, what should be said or done in the many contingencies that might arise.

On Sunday evening Madame de Groot then went to the wife of the Commandant, with whom she had always been on more friendly terms than with her malicious husband.  She had also recently propitiated her affections by means of venison and other dainties brought from Gorcum.  She expressed the hope that, notwithstanding the absence of Captain Deventer, she might be permitted to send the trunk full of books next day from the castle.

“My husband is wearing himself out,” she said, “with his perpetual studies.  I shall be glad for a little time to be rid of some of these folios.”

The Commandant’s wife made no objection to this slight request.

On Monday morning the gale continued to beat with unabated violence on the turrets.  The turbid Waal, swollen by the tempest, rolled darkly and dangerously along the castle walls.