“Ready?” asked Fee’s father. “Are you ready to bring us up?”
 
Fee nodded. She had sat at the controls of the family submarine many times before this, but you know how it is when somebody asks you to take over a submarine--you always feel just a little bit nervous.
 
“Yes,” she said, trying her best to sound brave. “I’m . . . I’m sort of ready.”
 
Both Fee and her twin brother, Ben, had been taught from a very early age to help sail the submarine belonging to their parents, who were well-known marine scientists. Now, at twelve, almost thirteen, Fee had enough experience to bring the vessel up to the surface all by herself. But it was a very big responsibility, and it always brought to mind the things that could go wrong.
 
What if you made a mistake and dived instead of surfacing? What if you surfaced too quickly, so that the submarine popped up out of the sea like a cork out of water? What if you came up right underneath a large ship--a massive oil tanker, perhaps--broke the glass observation window and then went straight down again? There were so many things that could go wrong in a submarine.
 
“Right,” said her father. “Take her up, Fee! You’ll do fine, of course, but I’ll be in the engine room if you need me.”
 
Once her father had left the control room she was quite alone. Her brother was doing his packing in his cabin, and her mother was busy in the galley--the submarine’s tiny kitchen--making sandwiches for the twins. Fee was by herself. Entirely.
 
Slowly she pulled the control column toward her. She could not see exactly where she was going--that’s never easy in a submarine--but she hoped there was nothing ahead of them, or above. The last thing a submarine wants to meet is a whale or a rock--or a whale and a rock, for that matter. You have to hope, too, that there isn’t another submarine coming up for air in exactly the same place as you.
 
A few minutes later, when they were just below the surface, Ben entered the control room.
 
“I’ve finished my packing,” he announced. “What about you?”
 
She glanced at her brother. She could see that he was excited, but she had far more important things to do than talk about packing.
 
“You mustn’t disturb me,” she said. “I’m just about to look through the periscope.”
 
He became quiet. It is always a special moment when you raise a submarine’s periscope, because that is when you find out where you are. You hope that you have come up in the right place, but you can never be absolutely sure. So if your hands shake a little as the periscope rises above the waves, and if you feel your heart thump a bit more loudly, then that is entirely normal.
 
Fee peered into the periscope as she pushed it upwards. There was water, just water, swirling round in every direction, and then, with no warning at all, she saw sunlight. The periscope was above the surface.
 
“What can you see?” Ben asked.
 
She blinked. The light was very intense and it would take a moment for her eyes to adjust.
 
You can turn a periscope round, so that it gives you a view in every direction. She would do that--just to check that nothing was coming--but first she would have a good look at the land.
 
“I can see an island in the distance,” she said. “I can see the shore.”
 
Ben caught his breath. “That’ll be Mull,” he said. Mull was the island they were heading for.
 
“It’s sunny,” said Fee. “It’s morning.”
 
“And Tobermory?” asked Ben. “Can you see Tobermory?”
 
“Which Tobermory?” asked Fee. “Tobermory the town or Tobermory the ship?”
 
She was right to ask: there were two Tobermorys. Tobermory, the town, was where the Tobermory, the ship, was based. They were going to the Tobermory, the ship, but Tobermory, the place, was the harbor in which she (and ships are always called she) was normally anchored. The Tobermory was a sailing ship and a school at the same time. It was a boarding school on the sea, and while most schools stay in exactly the same place all the time, this one did not. This one sailed about, teaching everybody not only subjects like history and science--the things that normal schools teach--but also everything that you needed to know if you were going to be a sailor.
 
“I can’t see either of them,” said Fee. “I think we might be a little way away. But we can’t be too far.”
 
“Let me have a look,” said Ben, sounding rather impatient. Although they were twins, Fee had been born two minutes before her brother, and that made her older. It was only two minutes, but she often said that those two minutes were very important. “When you’ve been alive two minutes longer than somebody else,” she was fond of saying, “it shows. You’re just a bit more grown-up, you see.”
 
Ben did not look at it that way. He thought he was every bit as mature as his sister, and felt entitled to do everything she did. Right then he felt that he should have a turn on the periscope. “Let me look,” he repeated.
 
“No,” she said. “I’ve spotted a seagull. Oh, it’s come down lower. I think it’s going to land on top of the periscope!”
 
Fee laughed as she watched the seagull land. She had a good view of its yellow feet. As she watched, it flapped its wings, sending little droplets of water splashing against the outer lens of the periscope.
 
Slowly she moved the periscope round, so that she could look in other directions. The seagull did not like this, and flapped its wings again in protest. Then she saw it.
 
‘There’s a boat coming straight toward us!” she cried out.
 
“Dive!” shouted Ben.
 
Because his sister was busy pulling down the periscope, Ben decided to take the controls himself. Pushing the column forward, he opened the throttle as far as he could. The submarine responded immediately, giving a lurch downwards.
 
It was just in time. Seconds later they heard the thud of a boat’s engine pass directly over them.