"You mean that the wave of energy really must be like a sword, stabbing one small hole through the barrier?"
"Exactly." A pause. "The time mirror represented just such a hole through the barrier. What appeared to us to be waves in the glass actually were frozen ripples in the space-time continuum—just as if you had dropped a stone in water, and the hole and ripples had frozen."
"Then when you looked into the mirror—"
"Your mind went out through that gap in the barrier. Ordinarily, of course, you would not even know that this was happening. But if your mind was concentrated on something in the past or future—as Elaine's was upon the picture of her ancestor—, you were automatically hurtled through time to that period."
The younger man frowned.
"Then why didn't my mind go, too, when Elaine's did? We both were looking into the mirror."
"But from different angles," the professor reminded him. "Remember, the actual break in the continuum was relatively small. Elaine, seated before the mirror, must have been directly in front of the gap, so she was sucked through. You, on the other hand—"
"Yes. I was standing up. Off center. So I didn't go." Mark nodded. "I see."
"And now," said the scientist, "the mirror is broken. Our last chance of saving Elaine is gone."
"No!"