Aiden, a curious fifth-grader, was busy working on his history assignment when he realized his trusty pen had vanished. He looked around his desk, shuffled through his backpack, and even checked the floor, but the pen was nowhere to be found.

"Hey, Justin, have you seen my pen?" Aiden asked his friend, who was sitting next to him. Justin shook his head, just as confused as Aiden. Suddenly, their other friend, Evan, spoke up.

"I think I saw Aiden's pen in the hallway earlier. It must have fallen out of your bag," Evan said. Aiden's eyes widened as he remembered that he had been rushing to class and may have dropped the pen without noticing.

Without hesitation, the three friends set out to investigate the mystery of the missing pen. They scoured the hallway, looking under lockers and in every nook and cranny, but the pen was nowhere to be found.

"This is so frustrating!" Aiden exclaimed. "That pen was my favorite, and I really need it to finish my assignment."

Just then, Aiden noticed a trail of tiny footprints leading down the hallway. "Wait, what's that?" he said, pointing at the strange markings on the floor.

The boys followed the trail, which led them to a small hole in the wall. Peering inside, they could see the familiar glint of Aiden's missing pen. "Aha!" Aiden cried. "It must have fallen into the wall!"

With some clever maneuvering, the boys were able to retrieve the pen from its hiding place. Aiden was relieved to have his trusty writing tool back, and the three friends congratulated themselves on solving the mystery of the missing pen.

"Great work, team!" Aiden said. "Now, let's get back to our homework."