If you play with fire, you may get burned

Crossing the torrent was a dangerous business, even with the boat, but the trio made it to the other side with only three near-death experiences and no actual deaths. After eating a rather damp lunch, they picked the little hull up and carried it along a narrow path to where Feet waited.

There they spent a placid afternoon, for Feet wanted all the news from the big city, and they were anxious to know what lay ahead. Among other things, Feet told them of an old castle in the pass above, where rich old Belvadere the Brigand had supposedly hidden his loot.

Not having any other business to attend to, Bert suggested that they seek the castle out, and try their luck at the treasure. Around mid-day the next day they first spied the ruins far above them, but distances are deceptive in the mountains and it was the following afternoon before they finally arrived.

They found the ruins empty, but for some crows and a couple circling buzzards. No furniture. Not even any woodwork, anymore. It had all been stripped off by travelers as firewood, judging by the large soot marks on the floors and ceilings of the more intact rooms. In one of these, though, there was still a wall of fine stone inlay [see attached image]. They paid it more attention than they might have, for it did not match what little decoration remained in the forgotten castle. It was not *of* anything, for one thing. It was instead made up of randomly selected triangles of stone, pieced together into a massive rectangle.

"Looks like a crazy quilt our granny made once," Al commented, "Except she couldn't have laid stone to save her life."

As they inspected this curious decoration, Bert suddenly bent and rubbed at the bottom of it.

"There's an inscription!" he announced, "All covered in dust and bird doings."

Curiosity overcame any niceness lingering from their stay at the palace, and the trio bent to rub the grime of ages away. Just as the light was starting to fade, their efforts produced the following inscription:

"Reach you into the fire's heart, for there lies golden glory.
But flinch you, or miss your mark, and there will end your story."

They studied this with interest, although the challenge did not prevent them from making fun of the verse.

"So what do you think it means?" asked Al. "Is the fire's heart one of these triangles? It must be . . . but I don't fancy poking all of them. For one thing, that bit of doggerel rather implies that nasty things will happen to you if you pick the wrong one."

Brian agreed. "If we can't figure it out, it might be worth poking a couple with a walking stick, but I don't think it's worth the risk. By all accounts Belvadere was a nasty fellow, who would probably grin in his grave to think of poor sods like ourselves biting it on his behalf after all these years. I have noticed that people with dreadful names are sadists, and Belvadere is borderline, at best."

So the three sat down to contemplate the mosaic in the dying light. It was almost dark when Bert picked up his walking stick, and poked one of the stones. There was a CHUNK and SCREE as ancient machinery shifted, and a number of the stones sank back into the wall.

Which triangle did he select, and why?

Solution