Seymour chuckled in reply, but declined to afford any information for the present. He suggested that Rigby should go outside and see if Anstruther had gone yet. Rigby came back presently with information to the effect that the burglar's outer door was locked, thus fairly assuming that Anstruther had executed his task and had gone. Seymour produced the simple apparatus by means of which he had entered the burglar's rooms on the last occasion.
"I am going to get that letter," he explained simply. "You need not have any fear about me. Open the window, please."
In less than five minutes Seymour was back again with the letter in his hand. He laid it on the table, and then proceeded to steam the envelope open with the aid of a kettle of hot water which he procured from the kitchen.
There was very little in the letter, but that little was to the point. The writer curtly commanded the recipient to meet him to-morrow night at a quarter to twelve outside the Mansion House Station of the Underground Railway. The recipient was enjoined to come prepared for business, and the last three words had been underlined. In the event of this being impossible, "Simple Charlie" was asked to procure a substitute, and let the writer of the letter know this not later than ten o'clock the next morning at the old address and in the old way. It was perfectly plain.
"You see exactly what this means," Seymour said. "I take it that the old address means Panton Square. But 'Simple Charlie' will have to tell me all about that in the morning. He shall write to Anstruther and put everything in order first. I have prepared a very pretty little surprise for Anstruther."
Seymour chuckled again, but refused to gratify Rigby's curiosity. He was taking no risks, he said; he even went so far as to seal down the letter again and return it to the burglar's rooms.
"We cannot afford to make a single mistake," he said. "Any little slip might ruin the whole delicate business."
There was nothing further to do, at least, so far as the night was concerned. It was getting very late now, and Rigby declined Seymour's offer of a whiskey and soda and cigar. He turned as though to go, and held out his hand to Seymour. Then he paused, as a sudden thought struck him.
"There is one thing we have forgotten," he said. "Don't you think it would be as well to take Bates into our confidence. We had arranged to do so really, but when we called an hour or two ago at Shannon Street police station he was not in. I don't know whether you agree with me or not, but I think he would be extremely useful to us just now."
Seymour nodded and chuckled. He seemed to be in the enjoyment of some good joke which he desired to keep to himself.