In the course of this year the prince's life was in serious danger.

A plot was laid to assassinate him on his way to Ryswyck, the leading conspirator being William van Stoutenberg, the younger son of Oldenbarneveldt.

Stoutenberg had, in 1619, been deprived of his posts and his property confiscated, and he wished to avenge his father's death and his own injuries.

The plot was discovered, but Stoutenberg managed to escape and took service under the Archduchess Isabel.

Unfortunately he had implicated his elder brother, Regnier, lord of Groeneveldt, in the scheme.