I want to scream, but instead I take that jolt of energy and transfer it to my running. My legs thrum, propelling me forward. I push thoughts of Mattie away. I gain on Joaquin and Dante. Like I always do, I concentrate on moving forward, on achieving my goal. And I keep running.

“Are you okay?” Cristina asks as she bites into her tofu. We’re at my nanny’s favorite Vietnamese restaurant. We eat here every Tuesday while we wait to pick up my little brother from his dad’s.

I never go to my dad’s house. I mean, maybe if I had ever met him, I would. But I’m not one of those kids with the split custody thing like Tristan—every Tuesday night and every other weekend.

I dip my eggroll in sesame sauce. Should I tell Cristina about Mattie? If I tell her about Matilde Gómez, though, she might tell Mom.

“I’m fine.” Instead, I tell her how I beat my best time in the mile run. “Six minutes, thirty-seven seconds.” I don’t tell her that even though I should be having the best day ever because I beat Joaquin again, I can’t get Mattie Gómez out of my mind. She’s ruining my day. I’m pretty sure she might be ruining my life, too.

After dinner, Cristina drives us back to pick up Tristan at his dad’s apartment. She waits in the driveway while I knock on the door to get my brother.

“Sorry, Mercedes,” Tristan’s dad says when he opens it. “He’s not ready yet. Come on in.”

This is what happens every week. Cristina waits in the car and I wait for Tristan. He’s never ready. This, as Mom always says, is all his dad’s fault. His dad is a nice guy but totally unorganized. His apartment is a disaster. Even if you don’t count Tristan’s stuff, which is scattered around the living room like a toy store exploded. A coloring book, one sock, two racecars, a packet of markers with the green and blue missing (his two favorite colors). While I wait, I study the pictures above the sofa, just like I do every time I’m here. The wall is covered in mismatched frames, each of them with photos of Tristan. There’s Tristan’s newborn baby picture; there’s him with his first tooth. There’s Tristan on a donkey at a petting zoo. There’s Tristan and his dad on a sailboat, and one of them squeezed together on a bus seat. I pretend not to be looking for the small frame at the far end of the wall. In it, a six-year-old Mercedes smiles with a baby Tristan. The hand on my shoulder in the picture belongs to his dad. I remember Mom taking this picture and thinking that Tristan’s dad was my dad.