This curious interview took place on the banks of the Forth near the Bridge of Stirling. Henderson was accompanied by Sir James Rollo, who filled the embarrassing situation of brother-in-law to both Montrose and Argyll.[11] Montrose, who knew from the Queen that these Covenanting overtures had been reported to his disadvantage in England, had taken care to be accompanied by good guarantees for his integrity. He came with Napier and Napier's son the young Master, with Keir and Lord Ogilvy. For two hours the interview lasted by the water-side. Montrose, professing to have lived lately too much in retirement to be aware how matters were going in the great public world, asked the Moderator what these offers meant, and what he was expected to do for them. Henderson, in the belief that he was talking to an apostate only anxious to find a plausible excuse for his apostasy, frankly admitted that it was intended to send an army into England to co-operate with the Parliamentary forces, and that in both countries it was resolved to push matters to the extreme against the King; and he urged Montrose to hesitate no longer, but to throw himself heartily into the good work, assuring him that he had only to state his terms, and that whatever they might be they would be accepted. Montrose then turned to his brother-in-law and asked if they came as the mouthpiece of the Estates, or only out of goodwill to him. Sir James answered that he understood the Moderator to have spoken by authority. But to this Henderson demurred. He was not exactly commissioned, he said, by the Estates, but he was sure that they would make all his promises good. "That will not do for me," replied Montrose. "I cannot commit myself in such important matters without the assurance of the public faith, especially when the messengers cannot agree among themselves as to the terms of their message."