This is a [SerialStory] with tags [SS] and [Subm] titled 'Submersible.'

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( Here is a link to part #1 so you can start at the beginning. )

( Find other items in the series - search 'Subm' | Find part 3 - search 'Subm_3' | Find other serials on SN - search 'SS_' )

When a woman uniformed similarly to doorman Silas and usher Melissa approached the base of the staircase, Thaddeus Tilney turned to Thiago Vasquez and goaded, "You have about 24 steps to solve the Great Riddle of the Door, my friend. I see a woman approaching who knows buttons, and knows how to use them."

His efforts to stoke urgency in Vasquez were immaterial. The man investigated coolly, narrowing the scope of possibility given the evidence available to him, muttering through pertinent logic chains as he gathered any clues to be found from the door, its frame, and transition.

When the woman reached the landing, Tilney bought extra time for Thiago anyway, greeting the concierge with his most pressing question: "What does this button do?"

The kempt woman was measured in her response, "I've specific instructions to inform all guests that the signaling devices will be explained in due time."

"Well what of the emergency button?" Tilney fired back. "I'd just press it but I wouldn't be rude."

"I've specific instructions to inform all guests that the signaling devices will be explained in due time."

Tilney's eyes narrowed, and her features came into focus. Dark brown hair with eyes perfectly matched. Light brown eyelashes. Eyebrows in between.... exactly in between... she was not human.

"However, there are a number of relevant data points I am at liberty to discuss..."

"Robot!" Tilney interrupted. It's body loosened and relaxed to default, per instruction, and per the R.E.D. consortium standards that had been in place since 2031. "Identify!" He ordered, but it did not -- in violation of same.

"Identify!" Thaddeus Tilney knew it was no use, that his voice had been detected the first time.

He and Thiago, then they and the Bosemans, looked at each other in quandary.

"No surprise that Forenza's robotica are state of the art, but I didn't expect we wouldn't know the difference," said Kevin, stating the obvious.

"Or that he'd jailbreak them," said Tilney. "Maybe he made them free himself," said Thiago Vasquez. Both comments implied a consortium violation by Frederic Forenza that would belie his compliant reputation.

The four shared stumped silence, until Tilney's curiosity won. He pressed the middle button, but nothing happened. He pressed it again, same result. He came close to pressing it a dozen times, remembered that sort of thing does not bring the relief sought, and pressed the bright yellow one instead. Here came the robot back to life.

After evaluation, it spoke, "There is no obvious emergency to attend to, Thaddeus. Please instruct."

Thiago Vasquez answered instead. "He couldn't wait for the presentation."

The robot wasted no time, "I've specific instructions to inform all guests that the signaling devices will be explained in due time. May I help you further, Thaddeus?"

"Spoil Thiago's riddle - and evening," he spat.

"ROBOT!" interjected Thiago Vasquez, and turned back to one of the doors. There were no handles, knobs, catches or latches. There were no buttons, switches, lights, or levers. There were no receivers, receptors, speakers or displays.

"Open?" He queried. No. He moved closer. "Open?" Nothing. He put his hand on the door. "Open?" No. He spoke into the fob. "Open?" Still closed.

"Thaddeus, tell me about this painting, how is it made?" Vasquez' had noticed something Tilney had not, having vision with no need for corrective lens.

Tilney furrowed, then squinted, then stepped close enough to touch it. He expected human achievement via artisan brushwork, but instead found cold symmetrical patterning. His work with AI involved imitation that could be indistinguishable from real, but here it was obvious enough for anyone to see. "It's not just unnnatural -- the telltale signatures of artificial intelligence have been exagerrated for effect."

Examining further, Thaddeus saw that the image was gradually morphing. First the impending technocratic advance of liquid circuitry creeped into the pure flower, then after far too long, it receded again just as slowly. After not enough untarnished time, rising concern came back again -- but the inclination then was to look away.

"It's an oily nanotech swarm in an endless loop -- a painting repainting itself," Tilney explained.

Thiago Vasquez considered. "I have a feeling these doors don't lead to areas meant for guests, my friends, but I have one more idea worth a try."

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WHAT OPENS THE DOORS? - Answer in the comments below. First correct answer wins the bounty.

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