But in the midst of Henry's active occupation of embarking his troops, danger was near him. A conspiracy to assassinate him was discovered at the very moment that it was intended to carry it into execution; and what is singular, the discovery came from the very person for whose special benefit the movement was intended.

The young Earl of March, as we have already had occasion to state, was not only the true heir to the throne, but had been brought up with Henry, and was really attached to him. The sister of the young earl was married to Richard, Earl of Cambridge, and brother to the Duke of York. Cambridge, by his alliance with the true prince, appears to have been infected with the ambitious desire of seeing himself not merely brother to a legitimate prince who was contented in his station, which, though that of a subject, was honourable and happy, but brother to a king. From the little light thrown by cotemporary historians on the progress of the plot, we can only perceive that Cambridge had sought the co-operation of several persons who were known to have acted or suffered in the opposition to the late king. These were Sir Thomas Grey of Heton, in Northumberland, and Lord Scrope of Masham, both of whom had been involved in the Percy insurrections themselves, or by their near relatives. Scrope was at this time high in the favour of his sovereign. He was his trusted chamberlain, and one of the most confidential of his privy council. In the chase and in his social hours, he was the chosen companion of Henry. Yet he appears to have given in to this base conspiracy, and Henry was to be assassinated before embarking, after which, the conspirators were to escape to Wales with the Earl of March, and there raise the banner of revolt in his behalf.

It would seem that the conspiracy was as ill-constructed as it was wicked. The conspirators do not appear to have obtained the decided sanction of the principal person concerned. Probably Cambridge might have speculated on private conversations with his brother-in-law, the Earl of March, and have persuaded himself that he would fall in with such a scheme when it appeared to him feasible. But when, at the moment of action, March was apprised of the intended blow, he refused, by the earnest advice of his man Lacy, to swear to keep the secret, but required an hour in which to consider of the proposal. However the persuasions of Cambridge or his own secret feelings might have inclined him at any previous moment, now, when his friend and noble patron Henry was menaced with instant death, March at once decided, and hastened to apprise the king of his danger. That March had listened to the voice of the tempter is plain from his first requesting a pardon from Henry for his giving ear "to rebels and traitors sufficiently to understand their schemes."

This pardon Henry at once accorded, but he seized the conspirators, and brought them immediately before a council, where their fate was to be decided by twelve jurors of the county. Grey pleaded guilty to the charge of having conspired to kill the king, "to proclaim the Earl of March, in case Richard II. was really dead," to having by their emissaries solicited the said Richard—or, as he was by the indictment declared to be, Thomas of Trumpington, who personated that monarch—to invade the king's dominions with a body of Scottish forces and Scottish lords.

Cambridge and Scrope demanded to be tried by their peers, whereupon all the lords of the army were summoned; the Duke of Clarence was appointed to preside in place of the king, and the Duke of York, that he might not sit in judgment on his own brother, nominated the Earl of Dorset his proxy.

Cambridge made an earnest appeal to the king for mercy, and Scrope pleaded, like March, that he had only listened in order to ascertain the objects of the conspirators, so that he might effectually defeat them. The plea did not avail him any more than the cowardly prayer of Cambridge. They were all three condemned, were led out to the north gate of the town, and had their heads struck off, just as the royal fleet, with a favourable wind, hoisted sail, and bore out of the harbour of Southampton on the 13th of August, 1415.

This memorable expedition, thus painfully inaugurated by the blood of treason in the very near kindred of the king, consisted of 6,000 men-at-arms, and 24,000 archers, which so many occasions had now demonstrated to be the real power of England. These troops were carried in a fleet of 1,500 sail; and, with an auspicious wind, entered the mouth of the Seine on the second day, August 15th. Three days were consumed in landing the troops and stores, and it does not appear that there was any opposition from the enemy.

Henry at once laid siege to the strong fortress of Harfleur, situated on the left bank of the river, and defended by a numerous garrison, under the command of the Sire D'Estouteville. The French knights of the garrison displayed the utmost bravery, and made repeated assaults on the troops of Henry while throwing up their entrenchments, but they were received in such a manner by the archers that they were soon very glad to keep within the shelter of their walls. These walls themselves were in bad repair; the succours which had been promised by the Government did not arrive; the English cannon was fast demolishing the outworks, and sappers were undermining the towers. A worse enemy than the English was also amongst them—the dysentery, owing to the dampness of the place, and the unhealthy quality of the provisions; and the garrison surrendered on the 22nd of September, after a defence of thirty-six days.

The success, however, was dearly purchased. The weather was extremely hot, and the place, lying low on the banks of the Seine, was at that season extremely unhealthy. A dysentery, partly from those causes, and partly from the incautious eating of unripe fruit, and the putrid exhalations from the offal of animals killed for the camp, broke out, and raged amongst the soldiers far more mortally than the awkward artillery of that age. About 2,000 of the troops had perished, besides great numbers who were disabled by sickness. Several officers of rank died, and when Henry had shipped off his sick for England, including the Duke of Clarence, the Earls of March, Arundel, and many other great officers, his army was reduced to about one-half of its original number.

A council of war, which Henry had called before shipping off his invalids, had come to the decision of returning wholly to England, and making preparations for the next year; but to this Henry would not listen for a moment. To embark altogether, he said, would look like fear, and convert their conquest into a flight. He was resolved, he added, to march to Calais, and dare every peril, rather than the French should say he was afraid of them. France was his own, he contended, and he would see a little more of it before quitting it. He trusted in God that they should take their way without harm or danger, but if compelled to fight, glory and victory would be theirs, as it always had been that of his ancestors in that country. He declared his route to be Normandy, Picardy, and Artois to Calais.