THEY MET THE NEXT DAY in Hero and Houndstooth’s suite to assemble the bombs that would drive the ferals to the Gate.

“So,” Hero said, staring into Archie’s saddlebag.

“The man I bought it from, Mr. Wolffenstein? ’E said you would know what it is. ’E called it ‘the Mother of Satan’?”

“Madre del Diablo?” Adelia asked. “I’ve heard of that before, I think. But I thought it was just a rumor.”

Hero took a rapid step away from the saddlebag. “No, no, it’s not a rumor at all, Adelia. Triacetone triperoxide.” They aimed a pointed look at Archie. “It’s extremely volatile.”

Archie shrugged. “Wolffenstein said it was so pure that it could be considered relatively stable.”

Hero pulled a single tiny white crystal out of the saddlebag and threw it to the ground. It exploded with a loud pop.

“ . . .’e said relatively,” Archie said with a shrug.

“Well then you can be the one to handle it,” Hero replied. “I hope you brought gloves.”

Archie pulled a pair of long leather gloves from the back pocket of her green breeches. “’Ero, darling, I always bring gloves.”

For the remainder of the afternoon, Adelia sat cross-legged on the divan, massaging wax into leather pouches, rendering them effectively waterproof. Archie filled each wallet with the tiny white crystals of madre del Diablo, then handed each one to Hero, who inserted wires and bits of metal in a configuration that seemed to make sense to them and them alone. Archie asked what Hero was doing, and the response was in no way illuminating.

“Would you like to discuss the inner workings of a blasting cap, Archie? Because we can discuss the inner workings of a blasting cap, if that’s what you’re looking for here.”

Archie had groaned and shoved Hero’s shoulder. “If you don’t want to tell me, then don’t tell me.” Hero had grinned and gone back to work, and Archie had caught Houndstooth beaming at them.

After Hero had finished doing whatever it was they were doing to make the bombs sufficiently dangerous, they wrapped each leather pouch around itself a few times. There was more room than they needed, since the crystals were so much smaller and lighter than the dynamite Hero had been expecting.

“You’ve worked out the equivalency, I suppose?” Houndstooth asked.

“More or less,” Hero replied. “We might get a little bigger bang than we expected, but I think it’ll all even out in the end. Don’t worry, Houndstooth. This hippo caper will go off without a hitch.”

Houndstooth opened his mouth to reply, and they all responded with him: “It’s not a caper; it’s an operation.”