Focaccia looked at the ground, where the window panel still lay. She stifled a sad smile.
"I don't know if I should say this or not, but Berry Batter did have a secret way into her room," she said. "Whenever the front door wasn't convenient enough, she would drape a curtain down from her window, and she could in and out that way." She looked back up and grinned slightly. "She's more mischevious than you might realize. I..." She hung her head. "I wonder what she did...on this night..."
Paladin sighed. "Well, that's what I came along with you in hopes of finding out. Let's see what we know, then..." He smiled. "And please bear with me - once I get going, I can talk forever, as Twilight can attest to."
"You said you talked with her at the fireworks show, and that you think you'd talked about the competition. After that, she apparently came back here. Which means she must have gotten here probably about the time that our unknown arsonist did, I believe. Out of curiosity, if she lives here, I assume she has her own set of keys?"
He rubbed his chin as he thought out the next part. "...The next part's the most important, and yet it's the one we can't seem to get together. ...The arsonist was targeting the storage room, specifically. That much is obvious from the... er... horrible mess in there. So that's most likely where they were. We know Firecracker Burst was also here, along with the missing wagon. Everypony had access to the Pizzeria because Alfredo left the keys in the front door."
Then another thought occurred to him. "...And if what you're saying is right, then even if we're wrong about Alfredo leaving the keys, then maybe they could have gotten in by a curtain left by Berry Batter. Either way, though, the keys ended up in the front door."
Paladin stopped a moment to collect his thoughts. "Twilight, do I seem to be missing anything so far?"