So, this question is about George R.R. Martin's Tuf Voyaging, the very first story's finale (The Plague Star).
Tuf lured Rica Dawnstar into a trap set by Jefri Lion for Kaj Nevis, but how did he learn about this trap? There is nothing in the text to suggest even a remote possibility of communication.
It's subtle but this passage shows Tuf finding the plasma cannon that Jefri Lion had set up (it's already been seen in the story that blinking is Tuf's only visible emotional "tell"):
Tuf drove through several kilometers of corridor. He was a cautious and methodical driver. At every intersection he stopped, looked right, looked left, and weighed his choices before proceeding. He turned twice, as dictated partly by stern logic and partly by sheerest whim, but stayed for the most part to the widest corridors. Once he stopped and dismounted to explore a set of doors that seemed interesting. He saw nothing, encountered no one. Now and again, Chaos moved about in his lap.
Then Rica Dawnstar appeared up ahead of him.
Haviland Tuf stopped his cart in the center of a great intersection. He looked right, and blinked several times. He looked left. Then he stared straight ahead, hands folded on top of his stomach, and watched as she came toward him slowly.
She stopped about five meters away, down the corridor. “Out for a drive?” she asked. In her right hand she carried her familiar needler. In her left hand was a tangle of straps that trailed down onto the deck.
For those who haven't read the story, this is an earlier scene:
Fortunately, plasma cannons had often been employed for automated perimeter defense, and this one had the standard minimind and autofire sequence. Jefri Lion erected the tripod in the middle of a broad corridor, approximately twenty meters down from a major intersection. He programmed in an extremely narrow field of fire, and calibrated the targeting cube with the utmost precision. Then he initiated the autofire sequence and stepped back with satisfaction. Inside the energy-pac he saw the plasma ball forming, burning brighter and brighter, and after a minute the ready light flashed on. Now the cannon was set, and its minimind was vastly quicker and more deadly accurate than Lion could ever hope to be firing manually. It was targeted on the center of the corridor intersection ahead, but it would fire only at objects whose dimensions exceeded certain pre-programmed limits.
