e was a big bank of slate-colored clouds, from
which, now and then, came low rumblings of thunder.

"I guess it won't be long before the storm reaches here," thought the
young pilot.

Almost before the boy realized it, an hour had passed. He was so
interested in steering the boat, and recalling the different points
that had been impressed on him by the pilot, that he did not notice
that Mr. Weatherby was gone much longer than he had said he would be
away.

"It's taking him a good while to get his medicine," murmured Nat. "I
hope he isn't going to be sick again to-night. I don't want to have to
steer the vessel among a lot of islands."

He was now anxiously awaiting the return of Mr. Weatherby, for the
storm seemed to be approaching more rapidly, and the darkness of the
coming night was added to by the black clouds, that now covered the
entire sky.

Nat shifted the wheel, to keep the vessel on the prescribed course,
and was looking ahead through the fast-gathering gloom, when some one
came into the pilot-house. He looked up to see Captain Turton, whose
face wore a worried look.

"I'm afraid we're going to have trouble," he said.

"How so, captain?"

"Mr. Weatherby is very sick. I was just in his cabin, and I found him
in a semi-conscious state. He had tried to take some medicine, but
before he could get it he was seized with a sudden fit of sickness. I
called in the doctor, and he said the pilot would not be able to take
charge of the vessel to-night. I don't know what we're going to do,
unless you can steer. Do you think you can?"

Nat hesitated. He had taken the freighter over this same course, when
Mr. Weatherby was in the pilot-house with him, but that was in calm
weather and daylight.

Could he steer the big passenger steamer over the same course after
dark, and with a storm coming up? It was a question grave enough to
make even an older person than Nat hesitate.

"It's a pretty big contract for a lad," said the captain. "I'll help
you all I can, but the rules require me to have a pilot in charge. I
can't do it, unless you feel that you can steer the ship, with such
help as I can give you. Otherwise, I shall have to put into the
nearest port, and I dislike to do that, as it will disarrange the
passenger schedule, and the owners object to that."

"I--I think I can do it--at least I'll try," said Nat, determined to
"keep his nerve" as the pilot had advised him. "I'll do my best."

"That's the way to