Among these was a person named St.Lawrence, Baron of Howth.

This man worked cunningly on the mind of the lord deputy, insinuating that O'Neill was plotting treason and preparing for a Spanish invasion.

He even went so far as to write an anonymous letter, revealing an alleged plot of O'Neill's to assassinate the lord deputy.

It was addressed to Sir William Usher, clerk of the council, and the writer began by saying that it would show him, though far severed from him in religion, how near he came home to him in honesty.
He was a Catholic, and professed to reveal what he had heard among Catholic gentlemen, 'after the strictest conditions of secresy.' The conspirators were, in the first place, to murder or poison the lord deputy when he came to Drogheda, 'a place thought apt and secure to act the same.' They thought it well to begin with him, because his authority, wisdom, and valour stood only in the way of their first attempts.

Next after him they were to cut off Sir Oliver Lambert, whom for his own judgment in the wars, his sudden resolution, and undertaking spirit, they would not suffer to live.