experience. My own experience tells me that
mental damage of this scope is almost always accompanied by other
symptoms when it is the product of a disease. No, I cannot credit the
idea of a pathogenic organism too seriously. It is as though some
outside agent pierced the cranium and cut off the control centers of
the brain."

"A dagger of the mind," Scotty murmured.

Chavez looked up sharply. "Yes! An ideal phrase for it."

Rick recognized the quotation from his school-work. _Macbeth_, Act II.
Another of Shakespeare's phrases from the same work leaped into his
mind. "Macbeth hath murdered sleep." Not Macbeth, but Marks. Rick knew
he wouldn't sleep well that night, nor for many nights to come.

Dagger of the mind! Well, it fitted. Watching the blank face of what
had been, only hours before, a brilliant scientist, Rick could feel
its deadly point himself.

CHAPTER X

Search for Strangers

The good weather turned bad, and dark clouds hung low over the New
Jersey coast. It was appropriate weather for the state of mind at
Spindrift. With Marks a victim of the mysterious "dagger of the mind,"
only Dr. Morrison remained of the original team.

The question, of course, was "Who next?"

At Hartson Brant's urgent request, Steve Ames visited the island and a
meeting of all staff was called in the big library.

Rick and Scotty sat on a library table, while the scientists occupied
the few library chairs. Steve Ames sat on Hartson Brant's desk and
acted as chairman for the informal session.

By mutual agreement, the girls had been excluded. Jan was nearly in a
state of shock over what had happened to Marks. Not only was she fond
of the crusty scientist, but she was fearful that the mysterious
ailment would strike her father next. And Barby was rapidly catching
the same fear. After all, new team members probably were not immune,
and Hartson Brant, Julius Weiss, and Parnell Winston were deeply
involved in the project.

Steve called the meeting to order. "Hartson, you suggested that I
come, which I was glad to do. Suppose you start by telling us what you
had in mind."

"Very well, Steve." The scientist's glance embraced his colleagues and
the boys.

"We have a problem that must be solved before we can continue with
calm and objective minds on the project that faces us. The problem is
simply, what is the ailment that has stricken three of us, and what is
its cause?"

Hartson Brant tamped tobacco into his pipe