e morning the girls decided to forego their usual game of tennis and
take an early dip instead. Nan had complained of an ache in the muscles
of her right arm, and as the trouble almost undoubtedly came from
overstrain, Walter had insisted that she take "a day off."

The weather had seemed uncomfortably warm at the hotel, but when they
reached the beach the girls were surprised to find that they felt
chilly.

"Goodness!" said Bess with a shiver, "I think I will let you girls go in
and I'll stay here. Experience has taught me that the beautiful green
ocean about these parts isn't always as balmy and warm as it's reported
to be."

"No, you don't," said Nan decidedly. "You know very well it spoils all
the fun if one of us backs out. Come on, Rhoda, you take the other arm.
One--two--three--go!" and Bess was hurried, half laughing and half angry
and wholly protesting, down to the water's edge and promptly ducked
under a foam-tipped, hungry, man-eating wave.

She came out on the other side and struck out manfully, puffing and
steaming like a young whale.

The girls watched her laughingly for a minute, then plunged in after
her.

"My, the water is cold," sputtered Grace, as the girls struck out
abreast with long, beautifully even strokes. "Poor Bess! I don't know
but what she had the right idea after all."

The hour being so early, the girls had that particular portion of Old
Man Ocean almost to themselves. There were a few early bathers, however,
and among these was a man with a long, thin face and a mouth that was
set in a hard, straight line.

Nan, doing the crawl with her head under water, came up directly in
front of this unpleasant-looking person and was so startled and
surprised in consequence that she almost forgot to keep herself afloat.

Her paralysis remained only a moment, however, and in a flash of time
she was swimming back toward her companions.

As for the man, having given Nan a careful look, he suddenly made a dash
for the shore and one of the bathhouses.

"I reckon this is my chance," he said, as he got into his clothing with
all speed. "I'll do the trick while she is in bathing."

Nan was almost out of breath when she reached her chums.

"Listen to me!" she gasped. "I've got to get up to the hotel--and at
once!"

"Nan Sherwood, is it serious this time, or is this only another of your
attacks?" asked Bess impatiently. "Here you are the one who dragged us
into the water at this early hour, an