"Does that couple look a little... peculiar to you?"
The bartender didn't make enough money to consider "observing passengers" as part of his list of duties, but he was willing enough to indulge his manager for a moment. He made a big, dramatic sweep of the hundred or so people in the Deck C Aft Bar both to placate his boss and to make his eyes falling across the couple seem less planned.
"There! In the yellow!" His manager spoiled whatever element of unintentionality there might have been by hissing into the bartender's ear and pointing across the way.
"They seem normal enough to me," he said with a service-industry smile. "Is there any reason to be nosy?"
"They just came out of a restricted stairwell a few minutes ago."
"You can't blame the passengers for being horny. 'A couple of brews, then off in twos' is my experience."
"Would you quit it," the manager snapped. "They weren't having sex. Something else is going on."
The bartender shrugged. Whatever that something else was, he wasn't about to figure it out by staring at his customers. He dismissed his manager with an "I'll let you know if I see anything funny" and went back to work taking orders and making drinks. He observed the couple to the extent of his pay grade - that is to say he served them a round of drinks and stopped paying attention.
A few hours later, after most folk - passengers and less rule-abiding crew - were well lubricated, a loud static crackling swept the ship and its lights went dark. From the restricted stairwell came a plume of smoke and s ight no one on the boat would ever forget.