Grotius returned to the Hague to serve the Republic in quality of Deputy to the States-General; but in a short time experienced a cruel reverse of fortune.  Being involved in the disgrace of the De Wits, he was stript of his dignities, and threatened with assassination; which determined him to leave Holland:  he went to Antwerp, where an attempt was made on his life.

He retired to Liege, and afterwards to Aix-la-Chapelle, and Cologn.  A general peace was at this time negotiating; and Grotius having done singular services to the Dutch Plenipotentiaries, he was permitted to return to Holland, after being two years absent.  He continued some time undisturbed in the country; but Wicquefort, the Duke of Brunswick’s Minister at the Hague, being taken into custody, among his papers were found several letters from Grotius, containing, it is said, some indiscreet things concerning state affairs, and against the Republic’s Ministers.  He was arrested and prosecuted.  Of the fifteen judges appointed to try him, nine declared him innocent.  This was in November, 1676.  Nicholas Heinsius, who was not prejudiced in his favour, writes to Graevius on the 6th of December following:  “There was certainly imprudence and malice in what Grotius did; but I leave others to judge whether he was guilty of high treason.”

It is improbable his judges would have shewn him favour, had he been convicted of a capital crime:  he was known to be hated by the Prince of Orange, whom the Dutch at that time sought very much to please.

Peter Grotius, thus escaping out of the hands of his enemies, retired with his family to a country seat he had near Harlem, where he spent the rest of his days in educating his children, and reading the best authors.  He died at the age of seventy.  Some pretend, but without foundation, that he was poisoned.  Those who knew him particularly speak of him as one of the best heads of his time.  “Peter de Groot, son of the great Grotius, was not so learned as his father, says Wicquefort; but I may venture to assert he was as able a Minister.  We can’t say too much of this man, who was above all praise.  I write this after receiving the news of his death.  How much is Holland to be pitied for losing a man who would have assisted in repairing the breaches made by the disorders which have for some years prevailed in the state!  He joined solidity of judgment to the graces of wit, and must have possessed these qualities in an eminent degree since they shone thro’ such a disagreeable figure.  It may be said of M. de Groot, that never did such a deformed body lodge such a fine and great soul:  he had a surprising ready wit, his conversation was delightful, his understanding clear and solid, and his sentiments just and equitable:  he possessed great knowledge of all sorts of business, foreign and domestic, and especially of what the French call the art of pleasing.”