On his first night on Indian Island, Dr. Armstrong dreams that he is in the operating room. It is very hot, and his hands are so clammy that it is difficult to hold the scalpel firmly. The thought crosses his mind that it would be "easy to do a murder with a knife like that...and of course he (is) doing a murder". Dr. Armstrong is surprised to note that the body of the woman on whom he is operating is "spare (and) meagre"; he remembers that it had been "a large unwieldy body". The face of the woman is hidden, and the doctor cannot remember for an instant whom it was he had to kill.
In Armstrong's dream, the handkerchief covering the woman's face is removed, and he sees that it is Emily Brent. He is relieved, thinking, "of course...it (is) Emily Brent that he (has) to kill". When he looks again, however, the face is different. This time it is Anthony Marston, who appears to be laughing, even though his face is "purple and convulsed". Anthony Marston is laughing so hard that he is shaking the operating table, and Armstrong tells his nurse to steady it. At that point, he awakens, to find Rogers standing over him, shaking him (Chapter 6, Part 1).