Under interrogation after her arrest, Ye Wenjie calmly admits that she killed two people at Red Coast Base on October 21, 1979: commissar Lei Zhicheng and her husband, engineer Yang Weining. She explains that the murders grew directly out of the day she received the Trisolaran warning and secretly sent her reply. Afterward, Lei summoned her and revealed that he had discovered the extraterrestrial message through a hidden monitoring program he had installed on the base computer.

Lei accused Ye of endangering humanity, but Ye realized he did not know she had already replied because she had bypassed the normal file interface. Lei then proposed concealing the incident instead of reporting it. He framed this as protection for Yang and Ye's unborn child, since Ye's actions would politically implicate her husband, but Ye immediately understood that Lei also wanted to claim the discovery of extraterrestrial intelligence for himself.

After leaving Lei's office, Ye decided to eliminate him. She loosened the receiver's ground connection so that the malfunction would appear to come from the dangerous grounding line that ran over a cliff. Because such repairs were difficult and risky, and because Lei habitually volunteered for visible frontline labor, Ye predicted that he would personally come to inspect the problem.

The plan worked: Lei arrived and went over the cliff on a rope to examine the grounding terminal. Ye dismissed the accompanying soldier so that she would be alone at the top, then prepared a makeshift hacksaw designed to leave an irregular cut. At that point, however, Yang unexpectedly arrived, concluded that Lei needed help, and descended on the same rope despite Ye's attempt to persuade him to use another line.

When Ye returned with a second rope, both men had already finished the inspection and were climbing back up, with Lei above Yang. Ye decided that she would never get another chance to protect her secret and her chosen path, so she cut through the rope. During the interrogation, she says she felt calm, believing she had found a goal to which any sacrifice could be devoted. She heard the men cry out and their bodies strike the rocks below, and later saw the stream at the foot of the cliff turn red.