Precedent

"Tanner," he called.
"Hurry up, down there," yelled the navigator. "Let's get on our way."
"Tanner. Come down here." Some thing in Manders' voice brought immediate action.
Tanner came scrambling down the tube, his face serious. "What is it?"
"Look!" Tanner followed the other's gaze, touched the thin stream of sticky stuff, held his hand closer to his eyes.
"Blood!" he breathed. "By all that's holy. Blood!"