I do not own Phineas and Ferb.
Phineas was bent over the blueprint, making little corrections to the mathematical equations. "Okay, I think if we do it like this, it should work."
There was a glint of light as Ferb keeled down next to him on the floor of the den. Glancing up, Phineas let out a small hiss. "Gah, dude, knock it off with the cross already. Sheesh."
Ferb shook his head, the silver cross around his neck swaying slightly at the movement.
It had been his birth mother's and as soon as the 'incident' had happened, he had fetched it from their room for his own protection.
"Come on, Ferb." Phineas set down the pencil. "Don't you trust me?"
Ferb looked up.
"Are-are you thinking about it?" He tried not to feel hurt about that.
Shaking his head again, Ferb pointed up. Perfectly timed with this was a thud and frustrated, wordless shout from upstairs.
"Oh," Phineas said, drawing out the word in understanding. "You don't trust Candace." He absently touched the side of his neck. "Well, I can't blame you there."
Ferb gave him a thumbs up and grabbed the pencil to make his own corrections.
"Don't worry. Once we have this built, everything can go back to normal." Phineas smiled, showing two little fangs. "Even if the abilities are pretty cool, the whole blood-sucking thing kind of ruins it for me."