Accordingly, one evening he got into Mary Stuart's room, and hid himself under the bed; but at the moment when the queen was beginning to undress, a little dog she had began to yelp so loudly that her women came running at his barking, and, led by this indication, perceived Chatelard.

A woman easily pardons a crime for which too great love is the excuse: Mary Stuart was woman before being queen--she pardoned.
But this kindness only increased Chatelard's confidence: he put down the reprimand he had received to the presence of the queen's women, and supposed that if she had been alone she would have forgiven him still more completely; so that, three weeks after, this same scene was repeated.

But this time, Chatelard, discovered in a cupboard, when the queen was already in bed, was placed under arrest.
The moment was badly chosen: such a scandal, just when the queen was about to re-marry, was fatal to Mary, let alone to Chatelard.

Murray took the affair in hand, and, thinking that a public trial could alone save his sister's reputation, he urged the prosecution with such vigour, that Chatelard, convicted of the crime of lese-majeste, was condemned to death.

Mary entreated her brother that Chatelard might be sent back to France; but Murray made her see what terrible consequences such a use of her right of pardon might have, so that Mary was obliged to let justice take its course: Chatelard was led to execution.