Up till the contemplated treachery of Arnold, the ascendancy of the British had been well maintained on the American Continent. Charleston had fallen and here André had twice risked his life disguised as a spy; the South was in British possession; Gates had been beaten at Camden and Manhattan was in their army's occupation. Arnold astutely chose the proper moment for his act of treachery, certain in that dark hour to produce a strong moral reaction upon the Revolutionaries. In September 1780 the American General forwarded to André a letter asking for a personal interview within the American lines, the Major to disguise himself as John Anderson. André refused to enter the danger zone and the meeting was arranged to take place at Haverstraw—neutral ground—on 21st September. Thereafter it became a matter of somewhat dangerous rumour that André, whose daring men well knew, was about to undertake a perilous enterprise, a successful execution of which must swiftly end the war. A baronetcy, a brigadiership, a large sum of money—these were the rewards Clinton is said to have promised his young Adjutant. It is generally agreed that André faced his present mission with anything but that imperturbability which had marked his departure on similar expeditions. He was saddened, it was said, by an indefinable presentiment of death and impending disaster, and left New York to keep his appointment with Arnold, sailing up the Hudson in the British sloop Vulture. Arnold had agreed to send a boat to the sloop at midnight, 21st September, in order to take off the Major, who, on his landing, was led by a friend of the former to the secret tryst on neutral ground. The interview was long, Arnold haggling desperately over the terms of settlement; dawn had already begun to shadow the eastern hill-tops and still the bargain was not square. By five o'clock, however, the men had come to terms, and Arnold, who had horses in waiting, suggested the completion of the details in documentary form at the house of a local farmer, Smith his name. André consented reluctantly, well knowing the house in question to be within the American lines. By ten o'clock the deeds were drawn up and signed; André was in possession of all necessary information concerning the post to be surrendered. Arnold was to make a show of resistance on the arrival of the British on 25th September, while Washington himself was to be delivered into the hands of the enemy on his return that way on September 27th. Benedict Arnold was to receive some £6500 as a reward for his treachery, a sum which was eventually paid though the surrender of West Point never took place.
On leaving Smith's residence and bidding adieu to Arnold, the Major discovered to his surprise that the Vulture had disappeared. The sloop had been cannonaded during the night and compelled to drop down the river. As the Major considered his difficult position, the vessel returned to its previous moorings and André requested Smith to convey him aboard. Smith refused, pleading reasonably enough that he was afraid of the consequences to himself of rendering such a service. No bribe being sufficient apparently to move the farmer, André found himself forced to remain where he was and to his undoubted peril, until nightfall. Smith offered to provide the Major with an American uniform, but finding it impossible to procure one, gave him instead an old-fashioned coat of the cavalier style, purple in colour, with faded gold lace. A melancholy beaver hat completed the strange attire of the British officer who covered the whole with an ordinary surtout. Contrary to express instructions from Clinton, André took away the papers which Arnold had given him at the farmhouse, concealing them in his top-boots—an entirely senseless as well as purposeless proceeding, which eventually led to his undoing. Accompanied by Smith and a negro, André crossed the Hudson at King's Ferry on 22nd September, rode boldly into the American lines, spending, indeed, a night at another farmhouse in the midst of the enemy. On the 23rd, bidding his companions adieu, the Major, following directions given him by Smith, made for so-called neutral ground which swarmed with Tories and where he might feel reasonably safe. Mistaking a turn, however, in the old Tarrytown Road, along which he rode his horse slowly and with some hesitation, he came suddenly upon a group of farmers who were ranging the countryside in quest of suspicious persons. One of them, Paulding by name, wore a Hessian surtout given him by a friend. When André came in sight the company was playing cards, and on the Major's approach, Paulding, the master spirit of the gang, stepped to the front, musket in hand, commanding the traveller to halt and account for himself. Seeing the Hessian coat—a garment peculiar to King George's troops—André stopped his horse.
"My lads," he said, "you belong to our side, I see."
"What side?" asked Paulding.
"The British side," André replied.
"We do," answered Paulding.
André was momentarily taken off his guard. "Thank God!" he exclaimed. "I am a British officer out on particular business. I am glad to be among friends once more and I hope you will not detain me."
"We are Americans," cried Paulding, "and you are our prisoner."
Assuming as much composure as he could, André drew Arnold's passports from his pocket permitting "Mr John Anderson to pass the guards to the White Plains," only, of course, to confirm the suspicions of the farmers, who thereupon dragged him from his horse, searching him from head to foot, duly to find the incriminating documents which clearly proved their captive a first-class spy. The Major began by offering them in turn, cash, his gold watch, one hundred guineas, and finally made a promise of one thousand guineas, saying he would remain a hostage in their hands till one of the party should return with the money. "We would not let you go for ten thousand guineas," shouted Paulding, and André's doom was spoken. He was taken to the nearest American post and delivered to the commandant, Colonel Jameson, under his name John Anderson. André at once requested that General Arnold should be notified that his friend "Anderson" was in custody, and the Colonel, an unsuspicious soul, concluded that he could best serve his superior officer by returning the captive to Arnold, under a guard of four troopers in charge of Lieutenant Allen, who was also entrusted with a letter in which the Colonel mentioned that he was "forwarding certain documents found on Anderson forthwith to Washington," and this was accordingly done. André, to his joy, set out with his escort on the return journey to Arnold's lines. Before the party had progressed many miles towards West Point, a messenger arrived with orders for their return, and André found himself a captive once more in Jameson's lines, the Colonel, on a subordinate's advice, having decided to refer the whole matter to General Washington. In the meanwhile Allen, of his own initiative, had proceeded to Arnold's headquarters with the private letter and report from Jameson to the commander at West Point. For this blunder your true American has never forgiven the simple-minded Colonel.
On 24th September, the day following his capture, Major André, of whose real name and rank the American officers were still ignorant, indited his famous letter to Washington, full of rhetoric and self-justification, in which he advanced several considerations for his release from captivity. Mentioning his name and military rank, he only wrote, he said, to vindicate his good fame, not to solicit security. He was not, he vowed with a strange distortion of actuality, accustomed to duplicity. He justified his negotiations with "a person" (Arnold, unnamed) who was to give him intelligence which should prove serviceable to British arms, a fair ruse of war, he thought. Having concluded these negotiations, he proceeded, he was conducted without his knowledge into the American lines. He had thus become a prisoner and was justified in his endeavour to escape by all means available, and having reached neutral ground, through a disguise, he had been arrested by irregulars. There were gentlemen at Charleston, he concluded, in a half-menacing and highly impolitic phrase, whose rank might be set in exchange for his; in any case they were persons whom the treatment he received could not fail to affect. Washington received this communication after the flight of Arnold who, learning from Jameson's letter, duly delivered by Allen, how perilously matters stood for him, had taken refuge on board the British vessel Vulture. The American commander-in-chief gave immediate orders for the transfer of André to West Point, where he arrived on 26th September, under the care of a strong escort commanded by Major Tallmadge, the officer who had advised Jameson to countermand the first order sending the prisoner to Arnold. It was to Tallmadge that André made the memorable confession that he had engaged in the adventure "for military glory, the applause of his King and country and perhaps a brigadiership." The Major asked the American in what light General Washington was likely to regard him.