The young detective gazed about in search of her quarry. To her annoyance he was not in sight.

“But he’s aboard,” Nancy said to herself.

She looked at the indoor lunch counter, but there was no sign of the pickpocket. Disappointed, she returned to the deck.

During the past few minutes there had been a sudden change in the weather. Now Nancy was nearly blown off her feet by a strong gust of wind.

As the boat churned through the choppy waves, Nancy scanned the clouds. They were black. She began to shiver in her thin sleeveless dress.

A few moments later, however, the young detective completely forgot her discomfort. She had caught a glimpse of the suspect near the port railing!

Before she could reach the man, a huge wave struck the ferryboat. Passengers were thrown off balance. Several women screamed.

The next instant there was a blinding flash of lightning, followed by a heavy roll of thunder. Rain came down in a torrent, blotting out all view of the river.

Gasping, Nancy tried to find shelter in the cabin, but others ahead of her jammed the passageway. In the milling throng she could no longer see the man she was following.

Suddenly, from off the port bow, came the deepthroated whistle of an oncoming boat. The ferry swerved sharply to avoid a collision, but not in time.

There was a terrific impact as the two craft crashed into each other. Flung sideways, Nancy went rolling down the tilted deck.

CHAPTER III

A Lost Formula

STRUGGLING to her feet, Nancy grasped the railing for support. Children were crying. Men and women were yelling as passengers trapped in the cabin fought to escape.

“Keep cool!” shouted a deck hand, trying to avert a panic. “We’ll reach the dock safely.”