Arnold's first plan was to receive André within the lines, and even at his own head-quarters, as a person devoted to the American interests, who had the means of procuring important intelligence from the enemy, and was disposed from patriotic motives to take some hazards in promoting so valuable an end. And here it may be observed, that this was a ground on which Arnold might proceed with safety, inasmuch as it was well known in the army, that the commanders resorted to every practicable mode of procuring intelligence, and employed secret agents in that service. Under this guise, therefore, all the preliminaries of a meeting with André were conducted as far as it was necessary to use the intermediate assistance of persons within the American lines.
At this time a detachment of cavalry, commanded by Colonel Sheldon, was stationed at the outposts on the west side of Hudson's River. Colonel Sheldon's quarters, with a part of the detachment, were at Salem. Lieutenant Colonel Jameson and Major Tallmage, with the remainder, were at North Castle. Notice had been given to Sheldon by Arnold, that he expected a person from New York, whom he designed to meet at Sheldon's quarters, with the prospect of opening through the agency of that person an important channel for procuring intelligence. Should such a person arrive, he requested Sheldon to show him proper civilities, and send information of the same to head-quarters at Robinson's House.
A letter was then immediately despatched to André, acquainting him with this arrangement, and telling him that if he could contrive to make his way to the American outposts above White Plains, he would meet with no obstacles afterwards, and would be secure under the protection of Colonel Sheldon, who was prepared to receive him. Whether André was deterred by the hazard of the undertaking, or any other cause, is not known, but he did not choose to pursue this course. He wrote a letter to Colonel Sheldon, however, dated at New York on the 7th of September, in which he said;
"I am told my name is made known to you, and that I may hope your indulgence in permitting me to meet a friend near your outposts. I will endeavor to obtain permission to go out with a flag, which will be sent to Dobbs's Ferry on Monday next, the 11th instant, at twelve o'clock, where I shall be happy to meet Mr. G———. Should I not be allowed to go, the officer who is to command the escort, between whom and myself no distinction need be made, can speak on the affair. Let me entreat you, Sir, to favor a matter so interesting to the parties concerned, and which is of so private a nature, that the public on neither side can be injured by it."
This letter was signed John Anderson, and was in some sort an enigma to Sheldon, who had not heard the name of the person expected from New York. Supposing it probable, however, that the letter came from the same person, he enclosed it to Arnold, telling him that his own health was such as not to allow him to ride to Dobbs's Ferry by the time appointed, and expressing a hope that Arnold would either go himself or employ some other trusty messenger.
Arnold replied to Sheldon in a very plausible way, but seemed a little embarrassed in clearing up the mystical parts of the letter, especially the passage about an escort, which appeared not to tally with the idea of a person coming out on such a mission as that, which was pretended to be the object of Anderson's visit. He said to Sheldon, that he had been obliged to write with great caution, and had signed his letter Gustavus, to prevent any discovery in case it should fall into the enemy's hands; that since there were several things in Anderson's letter, which appeared mysterious, and as Sheldon was unwell, and he had himself business at Verplanck's Point, he would proceed to Dobbs's Ferry and meet the flag. He added, that, if any occurrence should, prevent the expected meeting at Dobbs's Ferry, and Anderson should still come within the outposts, he wished Sheldon to send him word by an express, and also to permit Anderson to follow with an escort of two or three horsemen, giving as a reason that it was difficult for him to ride so far as Sheldon's quarters. As a farther cover, he requested Colonel Sheldon himself to accompany Anderson, if his health would permit; and even desired that his letters might be shown to General Parsons, who was expected daily to come from Connecticut, and take command of a body of troops in the neighborhood of Sheldon's station. All these particulars were artfully contrived to blind the eyes of such persons, as might become acquainted with the business, and to give it the air of a transaction for public objects.
André's letter to Sheldon, when divested of its disguise, will be seen to have had no other object, than to communicate the intelligence, that he should be at Dobbs's Ferry at a certain time. He presumed the letter would be sent to Arnold, who would understand its meaning, and conduct his plans accordingly. So it turned out. Arnold left home in the afternoon of the 10th, went down the river in his barge to King's Ferry, and passed the night at the house of Joshua H. Smith, who resided about two miles and a half from the Ferry near the road leading to Haverstraw. Early the next morning he proceeded to Dobbs's Ferry, at which place André had arrived according to his appointment, accompanied by Colonel Beverly Robinson, to whom the secret had already been entrusted by Sir Henry Clinton, probably at the suggestion or at least with the knowledge of Arnold. An accident occurred, which prevented the interview, and was near putting an end to the plot itself. When Arnold was approaching the point of destination by water, he was fired upon by the British gunboats stationed in that part of the river, and so closely pursued that his life was in danger and he was on the point of being taken prisoner. By some oversight the boats had not been withdrawn, or it may have been expected that Arnold would come with a flag, which appears not to have been the case.
Having landed on the west side of the river, he went down to the Ferry, where he remained till night. Whether André and Robinson were at the landing-place on the opposite side, or whether they came up from New York in a vessel and remained on board, has not been ascertained; but at any rate no meeting took place.
Not forgetting his accustomed caution, Arnold wrote a letter to General Washington while at Dobbs's Ferry. His passage down the river had been in so public a manner, that it could not fail to be known; and he feared suspicions might be raised concerning his motives and objects. Filling up the principal part of his letter with matters of some importance appertaining to his command, he said, as if incidentally, that he had come down to that place in order to establish signals, which were to be observed in case the enemy ascended the river, and also to give additional directions respecting the guard-boats, and to have a beacon fixed on a hill about five miles below King's Ferry, which would be necessary to alarm the country. These reasons were plausible, and afforded apparent proofs of his vigilance, rather than grounds for suspecting any sinister designs.
Being foiled in this attempt to mature his scheme of treachery, he left Dobbs's Ferry a little after sunset, went up the river in the night, and reached his quarters at Robinson's House before morning. André and Colonel Robinson returned to New York. Another appointment for an interview was now to be made, and the time and place to be fixed upon by the two parties; and in this a double circumspection was necessary, since it was known to Arnold that within a few days General Washington would cross the river at King's Ferry on his way to meet Count de Rochambeau at Hartford. It was essential, therefore, so to manage the business, that no suspicious intercourse should be carried on at that time between the lines, which should attract his notice or come to his knowledge.