but very soon she realized that the cloud was coming on and rising faster than her plane.

Below them the sea was still visible, a dull lead color now with greenish tipped white-caps. The wind had not reached the plane yet and the girls hoped that they might be able to keep ahead of the tempest.

Then it came, first with a gust that made the little ship bob and dance about. Terry knew this was only the beginning. The storm was upon them! The next deep breath of the hurricane would threaten their lives with its fury. Terry held her plane to the only course she dared to take. She was racing for dear life!

The throb of the motor told that the engine was being strained to the limit of its power. There was no time to lose. If the girls were to escape destruction, they must take that chance.

When the full force of the tempest struck the plane, it was tossed about like a straw in the wind. Under less experienced hands than Terry’s the plane would have crashed. Terry could feel the craft being shaken as if a mighty hand had taken it in its grip, as the gusts of wind struck vicious blows at the wings.

Terry’s grim face was set with determination. But her hand on the stick showed no sign of her fear, it did not tremble or lose its power to control. She was glad now that her father had insisted on training her in all the stunts of the air, for there was no possible position that her plane would take that Terry had not put it into deliberately above her own flying field, and brought it out safely.

But this was altogether different. There she had put the plane into those dangerous positions, now she was being forced into them and she never knew what was coming next.

Terry knew the danger she was in but she felt no panic. Every nerve was tingling, every sense alert. She knew she was doing her best. Her head was clear, her hand was steady and she kept the little plane, climbing, ever climbing.

The girl felt that Skybird was fighting for life, with what seemed like human intelligence. It shuddered and shook and it seemed to try to right itself after a gust of angry wind.

Prim clung to the cowling, terrified yet fascinated as she watched her sister. At times it seemed as if the plane had turned clear over, as if it were going down in a tail spin, but the next moment Terry would bring it up for a second. It was a big fight.

“She’ll win,” thought Prim. “She’s wonderful!”

Only for a second did Terry lose hope of victory. There was a sputtering of the engine that her trained ear heard. It sent a chill to her heart. Her hand shook. She gave a frantic glance back to see if Prim had heard that menacing sound. And that one look showed her a clear space in the dark masses.

The storm was passing. Terry held to the controls, praying that the engine would hold out until the wind ceased.

Suddenly Terry was able to put her plane into a steep climb that brought her above the storm. Coming out of that black cloud Terry saw Allan’s plane ahead of her. She followed it, her heart singing for joy. A mist came to her eyes as she realized that it was only by a miracle that both planes had gone through the storm and survived.

Terry signalled with the wings of her plane and was answered in the same manner. She followed Allan's lead, hoping that her engine would not go back on her. At intervals she heard a sputter that terrified her, but now the sky was clearing. She felt hopeful.

Allan finally headed east. This was strange. Terry looked at her compass and a frown came to her face. What was Allan doing? He was going far out of his way. At last she understood. Away in the distance was an island. He was going to land. She wondered if he were having engine trouble.

Terry did not dare to open her throttle wide. Any extra strain might be her undoing. But, as she neared the small island the plane ahead banked, circled and signalled, then went into a dive for landing on the far side of the island.

Terry tried to follow but the engine was sputtering once more. She made a long dive which brought her amphibian into the water at the near side of the island. There was a broad strip of sand and Terry sent her plane cutting through the spray on to the beach.

“We’re safe!” cried Prim as she nimbly stepped from the cockpit, followed by her sister. “Wasn’t that an awful storm?”

“It’s just luck that we’re alive. Now let’s go over and see the boys. It looks as if they might be having engine trouble, too,” replied Terry.

After making fast their plane by a rope to a palm tree at the water’s edge, the two girls scrambled up over the rocky ridge to the low summit. The island was narrow at this end and soon they were looking straight down upon a sheltered cove where the boys had landed and saw the amphibian floating on the water. A launch shot out from the shore and when it reached the plane, several bundles were dropped into the boat by the aviator, who then got out of the plane and was taken ashore.

The girls looked at each other, distress on their faces.

“We’ve followed a plane, but it’s the wrong one!” cried Terry. “What a stupid thing to do! Prim, how can you ever trust me again?”

“But I thought it was Allan and Syd, too,” replied Prim. “Never mind, these men will help us fix our plane and we’ll be off in an hour or two.”

With a wave of his hand the aviator started upward toward the summit where the girls stood.

“He seems to be friendly,” commented Terry. “But let’s wait here to greet him. How he’ll laugh when I tell him that I thought I was following another plane.” The girls waited at the summit until the stranger came up the winding trail. As they heard his footsteps Terry moved forward to speak, then grabbed Prim’s arm with a nervous grip. The man had come out on the summit and was staring at them with a triumphant grin. His eyes were glittering with a fierce and cruel light that made the cast in his eye more pronounced. It added to the sinister look in his face. The man facing them was Joe Arnold!

A moment later the girls gasped with dismay for their old enemy, Bud Hyslop, came shambling up the trail.

“Well, look who’s here!” said Bud and added sarcastically, “this is a pleasant surprise!”

But Joe silenced his rough-neck follower with a scowl and a low snarl. “Don’t get funny. Shut up!”

Joe Arnold, with menace in his voice, addressed the girls, “Why did you come here?” he demanded. “What do you want?”

Terry stammered for a second then answered: “I was having trouble with my engine after that storm and I knew I’d have to come down, so I followed you here.”

Joe stared at the girl and shrugged his shoulders. “That sounds fishy to me. I think you’re trying to spy on me. What brought you away down here?”

“We’re on a vacation,” answered Terry. “We are on our way to the Canal Zone.”

Joe