“Hello,” I called quietly, and then pushed it open. Zac was sitting on the floor, surrounded by dozens of batteries that he was busy attaching together with wires.

“What you doing?” I asked.

“I am going to create the world’s biggest battery, and then I’m going to be in the Guinness Book of Records.”

“I bet you are.” I sat down on the floor next to him. “Can I help?”

He nodded, and then showed me what to do. We sat in silence, working for a while before I spoke.

“I’m really sorry about last night. I lost my temper and it wasn’t cool. I shouldn’t have shouted at you like that.”

He stopped what he was doing and looked at me. “Who was on the phone?”

I sighed. “Just this lady.” I brushed it off.

“From where?”

“From this place that I wanted to study art.” My stomach knotted.

“Why do you need to study art, you are so good at it already. You should also be in the Guinness Book of Records.”

I gave him a smile. “Thanks. But I reckon you’ll make it into the Guinness Book of Records before I do.”

He observed me for a while. “Probably.” And then he looked back down and continued making his battery.

“So, are we cool?” I asked softly.

There was a long pause between us, and I waited for him to speak again. Waited for him to forgive me. “Can you google Tutankhamun and tell me about him?” he finally said, breaking the prolonged silence.

“Sure.” I pulled my phone out, went to Wikipedia and scrolled. “Look at this.” I turned my phone around and showed Zac. “This is made of pure gold.”

Zac leaned in. “Is that his face?”

“I think so.”

Zac studied the face for a while. “You know gold is the best conductor of electricity.”

“I didn’t know that.” I put my phone away and carried on attaching the batteries to the wires. “Maybe,” I leaned over to him and whispered, “we should borrow some of mom’s bangles and attach them to this giant battery and see what happens?”

At that, his face lit up. I smiled. I loved it when his face lit up like this. When his mind grabbed onto something that interested him. When something deep inside that diverse web of firing, flickering neurons sprang to life in a way that I would probably never understand. But then his face fell.

“What?” I asked.

“Promise you won’t be mean to me like that again?”

My heart thumped in my throat. “I promise.”

“Promise?” he repeated.

“Cross my heart,” I said.

He looked confused and I quickly realized my mistake.

“What does cross your heart mean? How do you cross your heart? With what?”

I shook my head and smiled. “Never mind, it’s a stupid saying.”