At 10:47, the back wall of Lee's Pharmacy shimmers.

  It's subtle. If I weren't staring directly at it I'd miss it - a ripple in the brick like heat haze, except it's April and fifty degrees. Then a shape pushes through. Not breaking, not crumbling. Just - moving through the wall like the wall is water and he's wading.

  He's skinny. That's the first thing I notice. Skinny and not very tall, in a dark hoodie with the hood up and a bandana over the lower half of his face. Backpack slung over one shoulder. He phases the rest of the way through and stumbles slightly on the other side, catching himself against the dumpster. His hands are shaking.

  He's a kid. He's a scared kid in a hoodie who just walked through a wall and his hands are shaking and there are two NSRA agents sitting in cars sixty feet away waiting to catch him.

  I'm off the roof before I've finished thinking about it. The drop is twelve feet - I roll on landing, absorb it with my knees, come up moving. The alley is narrow and dark and I'm between the kid and the street-side exit in about three seconds.

  He sees me and freezes. The backpack slips off his shoulder and hangs from one hand. His eyes go wide over the bandana - I can't see the rest of his face but the eyes are enough. That's terror. That's a sixteen-year-old looking at a figure in tactical gear and a shark helmet who just dropped out of the sky and landed between him and the only exit he knows about.

  "Don't run," I say. The voice modulator makes it come out low and flat, which is probably not helping. "I'm not here to hurt you."

  He takes a step back. His outline flickers - that shimmer again, his body trying to phase on instinct. Fight or flight, and flight for him means becoming intangible. If he phases now he'll go back through the wall and into the pharmacy and then what? Out the front door, straight into Torres?

  "Stop," I say, and I hold both hands up, palms out. "Listen to me. There are people watching the front of this building. Two cars. Federal agents. If you go back through or out either end of this alley, they'll see you."

  The flickering slows. He's listening, or at least he's too scared to commit to running.

  "Who are you?" His voice is muffled by the bandana, but I can hear the waver in it. Young. Definitely young.

  "Megalodon. I'm--" How do I explain this in ten seconds? "I'm not a cop. I've been investigating the same pharmacies you've been hitting and I came here tonight because I figured out this one was next. So did they."

  "Tasha's voice in my ear: "Sam, the lot car just turned on its headlights."

  My stomach drops. "How long?"

  "Could be nothing. Could be a check-in. Could be they're about to do a sweep."

  I look at the kid. He's frozen, one hand on his backpack strap, eyes darting between me and the wall he came through. His outline is still flickering at the edges, like a bad signal.

  "What's your name?" I ask.

  "What?"

  "Your name. I need you to focus."

  "I - why do you--"

  "Because I'm about to help you get out of here and I'd like to know what to call you."

  He swallows. "Marco."

  "Okay, Marco. The stores in this strip mall share walls, right? Nail salon, cell phone shop, laundromat, then Lee's on the end?" I point out. I don't have time to do the full dialogue with him.

  "I - yeah?"

  "Can you phase through sideways? Not out the back of the building, through the walls between the stores? Horizontally?"

  He blinks. I don't think he's thought about this before. "I... yeah. I've gone through interior walls before. It's easier than exterior, actually - they're thinner."

  "Good. Here's what you're going to do. You're going to go through Lee's wall back into the pharmacy, then through the interior wall into the cell phone shop, then through into the nail salon, then through into the laundromat. Exit from the laundromat's back door on the far end of the strip mall. By the time someone calls 911 about a kid running through their store, you're three blocks away and nobody knows which direction you went." I lay it out as fast as I possibly can.

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  "Movement," Tasha pipes. I feel sweat prickling the back of my neck.

  "What about you?" Marco, 'Marco'? Is that his name, or a Marco Polo joke?-- asks.

  "Don't worry about me," I tell him.

  "You just jumped off a roof."

  "I do that a lot. Go. Now."

  He hesitates for one more second. I can see him doing the math - trust the stranger in the shark mask or take his chances with whatever's out front. The flickering in his outline steadies. He's made a decision.

  "The pills in there are cut with something," he says, fast, like he's paying me back before he leaves. "I'm not doing this for fun. I don't need the Jump. I'm just not letting them fuck with my neighborhood anymo--"

  "Don't justify yourself to me. Go. If you need me, find me at the Tacony Community Center. Not in costume," I say, sort of shooing him away with my hands. "Skedaddle."

  He nods once, turns, and walks into the wall. Not through it - into it. There's no shimmer at all - just the disconcerting view of a human body clipping into brick like the brick is... I don't know, fake? A sort of brick-painted fog? Nothing moves. He's just... absorbed into the brick like he was never there. I can hear - or maybe I imagine I can hear - a faint sound from inside. Movement through partition walls. A kid phasing sideways through a strip mall at eleven PM on a Wednesday because I told him to.

  "Sam," Tasha says. "The street car just opened a door."

  I'm alone in the back alley.

  Marco is gone - horizontally, invisibly, threading through store walls toward the far end of the strip mall where nobody is watching. By the time he emerges from the laundromat he'll be a kid in a hoodie on a dark street and there's no way to connect him to what just happened inside Lee's.

  But I'm standing in the alley behind a pharmacy that was just broken into, in a blue and white shark costume, with no ability to walk through walls.

  Footsteps. Coming from the lot side. Someone moving with purpose, not running but not strolling either. The careful pace of someone who heard something and is checking it out.

  I look up. The roof I dropped from is twelve feet above me. I can make the jump - grab the gutter, pull myself up, roll onto the roof. I've done it a hundred times. It takes about four seconds.

  Footsteps getting closer. I can hear a second set now, from the street side. They're closing the alley from both ends. Standard sweep pattern - one from each direction, meet in the middle, clear the space.

  I jump. Grab the gutter with both hands and it's old aluminum and it groans under my weight but holds. Pull up, elbow over the edge, one knee on the roof membrane -

  Flashlight beam sweeps the alley below me. A second later, a second beam from the other end.

  "Clear," a voice says. Male, professional, clipped. "Nothing in the alley. Check the back wall."

  I'm flat on the roof, not breathing, staring at the sky. The gutter is still vibrating from my weight. If either of them looks up right now -

  "Back wall's been breached. Same as the others. He came through here." That's Torres. I recognize the voice now - calm, methodical, a little tired. The voice of a good agent on his third night of stakeout duty who just missed his target. "Perimeter's clean. He's gone."

  "How? We had the front and the side."

  "He went through the interior walls. The stores share partitions. He could have exited from any unit in the strip mall."

  Silence. Then the partner: "Damn."

  "Yeah," Torres says. I can hear something in his voice that might be frustration or might be grudging respect, hard to tell from a rooftop. "Call it in. We need to adjust the coverage model. This kid's learning."

  I lie on the roof of the laundromat and breathe. The stars are out - you can see like four of them in Philly, which is sad if you think about it - and my heart is doing something aggressive in my chest and I'm seventeen minutes past my revised curfew.

  "Tash," I whisper.

  "Do you need me watching the kid or the agents?"

  "Kid."

  "Roger," Tasha sort of sighs. I hear footsteps behind me. Behind-under, since I'm lying down. Then, they stop. Tasha's voice is crinkly in my ear.

  "I caught a figure exiting the laundromat's back door about ninety seconds ago. Hoodie, backpack, heading east on foot. Lost him after two blocks. No pursuit."

  Marco made it.

  I close my eyes for one second. Just one. Then I sit up, check the alley below - empty - and start moving. Three rooftops north, fire escape down, side street east, and I hit Frankford avenue in my civvies, pulling out my phone just long enough to distract myself.

  I text Mom: Coming home now. Safe. Sorry I'm late. Not a fight.

  Mom texts back: We'll discuss it.

  Dad texts: Your mother is using her quiet voice. Good luck.

  There's a crack behind me. I stop. An audible little crackle, almost like a clip of a split second of a flame in a backyard.

  "Don't move," Agent Torres says, pointing what I assume is a taser at my back. "This model's great at penetrating clothes."

  The car pulls up aside me and rounds the corner, quickly shoving itself into very illegal street parking sort of where the storm drain is, close to a fire hydrant. Agent #2 - not Agent Jennings, someone else, did she get promoted or does she just not work in Philly anymore? Or what? - steps out. This one's another guy. Sort of a little fat but not in the way that makes him look obese. But not quite a power lifter either. Just like... a little out of shape, without cool sunglasses, Black, short buzzed hair.

  "You like penetrating teens' clothes, Torres?" I ask, raising my hands up above my head and lacing my fingers, resting them on my hair.

  "What, how did-- Small?" he asks, presumably at the exact moment that the voice recognition hits. "What the fuck are you doing here?"

  "I ask myself that every day, Agent," I quip back. Cool. Awesome. Loving life right now.