While Maria Park and Charity Singh disagreed on many things, including Maria''s innocence, they shared a conviction that the world operated by certain rules. It was inconsiderate of these two revolvers to both exist at the same time.


    Felicity, at least, was taking it in stride. Common sense was fine, but logic and deduction and all that jazz seemed overrated to her when compared with honed instincts.


    "This sure looks like a setup, but my gut says it doesn''t add up," said Felicity. "If this forger''s smart enough to make a fake gun, why weren''t they smart enough to keep me from showing y''all the original?"


    "Maybe this person didn''t know you were keeping it safe," said Maria. "Maybe... they planned to ambush me and get rid of mine." The thought made the hairs on her neck prickle.


    "Nah. If that were true..."


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    Narration Unlocked by librarysmiles:Keep it Simple


    "...a person planned to ambush you and take your gun. But hey, then they''d have your gun, yeah? So why not just use THAT for the murder, not a copy?"


    Felicity tapped her temple with a fingertip.


    "That''d be way simpler. Lot fewer ways to get caught, too, than if they tried to forge something."


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    "Forgery may have been unlikely," said Agent Singh, with a hint of strained patience, "But anything else is just impossible."


    "Yep. Seems like it," said Felicity, "But what did Sherlock say? Once you eliminate the improbable, whatever''s left, no matter how impossible, has got to be true."


    "Um, that''s sort of the exact opposite," said Maria, "of what Sherlock Holmes said."


    Felicity''s attempt at explanation shut down, Agent Singh made a closer comparison of the revolvers. Though identical in serial number, they differed in two respects. First, the gun found on the scene had been fired recently, and three of its chambers held empty cartridge casings. Second, fine traces of powder were trapped in some of its cracks.


    This called for forensics.


    Though a culprit might deface a serial number, they could never forge a gun''s ballistic properties. The imperfections in a revolver''s barrel score tiny ridges into bullets that pass through it, a permanent record of their passage. All that was necessary was to fire a test shot from each revolver into a block of ballistics gel, then compare those bullets to the one in Palmstroem''s corpse. A match would reveal the real murder weapon.


    "Jeff, when you get to the lab, tell them to limit it to one test firing each," said Agent Singh, motioning over her assistant as she filled out the evidence transfer paperwork. "We don''t want to foul up the barrels too much. Fingerprint and scan them, too."


    Maria tried to reassure herself that this would only help her case. She hadn''t touched it. Unless... could the murderer have also forged her fingerprints?


    "Send these to lockup when I''m done?" asked Jeff as he signed the guns into his custody.


    "Yes -- wait, no. Bring them back to me afterwards," said Singh. "I''ve got a test of my own to do."


    The assistant agreed, accustomed to Singh''s improvisational approach to investigation, and left. Agent Singh was now alone with Felicity Crowe and Maria Park, and that, in her eyes, was still one person too many.


    "Ms. Crowe, I think we''re almost done here. There''s just one last thing I need to check. Show me your walkie-talkie."


    Felicity unclipped it from her belt and passed it to Agent Singh, who pushed the settings button and skimmed the menus.


    "I see two programmed presets. Two different pairings?"


    "Yup," said Felicity. After the tangled mess with the guns, it was reassuring to be talking about something that made sense. "Preset D for my day job, preset N for my night job."


    "It''s set to D," said Agent Singh.


    "Yeah. Guess that''s why Maria couldn''t contact me. Must''ve forgot to reset it." Felicity punctuated her claim with a much too-offhand shrug.Unauthorized content usage: if you discover this narrative on Amazon, report the violation.


    "Or you changed it afterwards," replied Agent Singh. "To back up her story. You didn''t test your equipment when you started your rounds?"


    "Well, no. I was in a hurry. Got in a little late."


    "Late? Why?" Agent Singh pulled out the keycard records and jotted down a note. So far, this looked consistent. Maria had started her rounds well before Felicity had even arrived.


    "A little trouble at my day job. A guy didn''t want to leave. He got kind of violent."


    Later follow-up would reveal that hospital furniture had been thrown, windows had been broken, and, in violation of good biosafety practice, break room dishrags had been used to sop up blood. Nobody died, though, and as Felicity reckoned things, that meant that she oughtn''t to make a big production out of it.


    "So, sure, I guess I was sorta out of it that evening."


    "I wish you''d mentioned it to me," said Maria, feeling a little ashamed that she''d found her friend''s lateness suspicious at the time.


    "Eh, it wasn''t the end of the world."


    "I''ll confirm your story with your supervisor," said Singh. "In the meantime, you''re free to go. But stay available by phone. If I call at any time tonight, you''d best pick up, or your front door comes down." She said this as if she were threatening a minor inconvenience rather than a no-knock raid.


    With a frown of dissatisfaction and worry, Felicity gathered what little remained of her possessions now that the gun and walkie-talkie were federal evidence. "Remember," she said to Maria, "Don''t blab until a lawyer gets here. At least, no more than you already have." On the one hand, she regretted leaving her partner to face the music alone, but on the other, what could she do?


    "I''ll just tell the truth," said Maria.


    "No way, that''s how they get you," said Felicity. "The truth can sound awfully bad."


    This sage advice dispensed, Felicity took the elevator down, and the lobby cameras recorded her as she departed the Saturn Technologies building without looking back.


    Maria and Agent Singh were alone again, though Maria knew that this privacy was only an illusion. If she set one foot out of place, federal agents would be in the room in a snap, cuffing her up and pinning her to the most convenient surface.


    Wordlessly, Singh rose to her feet, pulled a flashlight from the big box near the table, and motioned for Maria to follow.


    They returned to Uncle Johann''s cluttered office. Where his body had lain two hours before, only a bloodstain and a string outline remained. Tiny number placards had been set up to allow the photographing of evidence in place. The pillow was still on the floor, the papers still scattered, the puddle of blue-green liquid in the corner -- it was all too much for Maria.


    When she had first found the body, she had surveyed the crime scene methodically, with an almost unreal clarity. But that self-possession had been mostly born of denial, and was now gone.


    "You''re hyperventilating," said Agent Singh.


    That was true, Maria realized. She was hyperventilating. She forced her breathing to steady. "I''m fine."


    "Do you see that puddle in the corner?" said Agent Singh. The blue-green liquid was fairly obvious against the carpet. If the tipped-over bottle next to it was any indication, it looked to be the same bottle Maria had brought over from the machining room.


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    BLOCKING INTERACTION: Not all of the antifreeze traces may be immediately obvious. What can be done to check the scene more throughly?


    The remainder of this chapter is locked until this puzzle is solved.


    A clue may be found in an earlier chapter. (UNLOCKED.)


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    Narration Unlocked by Librarysmiles:


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    With gloved hands, Agent Singh flipped off the light switch and closed the door. Since the hall lights filtered through underneath, the crime scene was far from pitch black. It was still too dark for Maria''s comfort.


    Singh turned on her ultraviolet flashlight, and a deep purple beam passed over the floor until it reached the puddle, which glowed noticeably. "There''s the main pool…”


    Maria watched as the beam moved to the edge of the splatter and beyond. What had been invisible before was now revealed: a set of irregular footprints. Someone had tracked antifreeze over the carpet. Following the track, it was as if this person had stepped hurriedly out of the puddle, made a few quick strides to the middle of the room, and then moved erratically, sometimes sideways, sometimes back.


    "The struggle," said Maria. "That must have been the struggle!"


    "They don''t match your Uncle''s feet. Now, give me your right shoe.”


    Maria crouched awkwardly, not wanting to touch anything, and removed the shoe as directed. Agent Singh took it and shone the UV flashlight on its sole. No glow. Then she checked its size against the footprints. The shoe was too small. Satisfied, she tossed it back to Maria, who nearly fumbled the catch.


    "I didn''t expect a match, to be honest," said Agent Singh. "But checking did no harm." She turned the lights back on.


    For the first time that night, hope shone in Maria''s eyes. "Wait, if they don''t match either my Uncle or me, doesn''t that prove I was telling the truth? Somebody else was here! A third person was in the wing!"


    Agent Singh shot Maria a look of disbelief. Surely she’d noticed the obvious! “You don’t see anything wrong with those footprints?”


    Maria looked again. “Oh.”


    Footprints went to the center of the room and milled about… but none left the room.


    “That’s right. Unless your mystery culprit took off his shoes or cleaned them somehow, those prints must be fake.”


    But that wouldn’t dissuade Maria so easily. She’d seen her opening, and she planned to make the most out of it. “Even if they’re fake, it still couldn’t have been me! I wouldn’t have had time to fake them!”


    If she had expected this argument to produce any effect on Agent Singh, she was soon to be sorely disappointed. “I assume your argument is that Felicity came running as soon as she heard the shots, leaving you no time to tamper with the scene. That’s what you intended to say?”


    “Yeah!”


    “…Follow me,” said Agent Singh, sighing. “I want to show you something.”


    Unsure of what lay in store, Maria accompanied her into the elevator. It began to ascend.