Before she could reply the man had turned and was hurrying away.
Olga opened the note, her heart beating furiously. It was utterly blank. At first she thought it was a hoax. Then she happened to remember that there was such a thing as invisible ink. At last! Hargreave was alive; this letter settled all doubt in her mind on this question. Alive! And not only that, but the girl and Jones were evidently in communication with him. She summoned a waiter, made a secret sign, and he bowed and approached. She slipped the letter into his hand and whispered: "Show that at the cave to-morrow. It is in invisible ink and meant for Hargreave."
"He's alive?"
"Positively."
"Very well." The waiter bowed and strolled away nonchalantly.
Braine was in Boston over night, otherwise the countess would have taken the mysterious note at once to him. She remained for perhaps a quarter of an hour longer and then left the garden. She would have taken the letter to her own apartment but for the fact that the chemicals needed were hidden in the cave.
Now it happened that Florence went out for her early ride the next morning, and crossing a field she saw a man with a bundle under his arm. The sun struck his profile and limned it plainly, and Florence uttered a low cry. The man had not observed her. So, very quietly, she slipped from the horse, tethered it to a tree, and started after the man to learn what he was doing so far from the city. She would never forget that face. She had seen it that dreadful night when the note had lured her into the hands of her enemies. The face belonged to the man who had impersonated her father.
It occurred to her that she might just as well do a little detective work on her own hook. She had passed through so many terrifying episodes that she was beginning to crave for the excitement, strange as this may seem. Like a gambler who has once played for high stakes, she no longer found pleasure in thimbles and needles and pins. She followed the man with no little skill and at length she saw him approach a knoll, stoop, apparently press a spring, and a hole suddenly yawned. The man vanished quickly, and the spot took on again its virginal appearance. A cave. Florence had the patience to wait. By and by the man appeared again and slunk away.
When she was sure that he was beyond range, she came out from the place of concealment, crept up the knoll, and searched about for the magic handle of this strange door. Diligence rewarded her, and she soon found herself in a large, musty, earth-smelling cave. Loot was scattered about, and there were boxes and chairs and a large chest. Men evidently met here, possibly after some desperate adventure against society. She found nothing to reward her hardihood, and as she was in the act of moving toward the cave's door she beheld with terror that it was moving!