Disclaimer: I do not own Percy Jackson (or any of the relating, appropriate characters). Complete control of the "Heroes of Olympus" franchise falls under the ownership of Rick Riordan, author of the "Percy Jackson" series.
Kronos approaches the magical boundaries of Camp Half-Blood, and after some magical resistance from the force field, pushes through. Although he had only broken out of Tartarus less than 7 hours before, he has assumed a human form and regained most of his strength. However, he still cannot remember who he truly is... only his profound attraction for Annabeth... Chase, wasn't it? Using his human form to blend in with the surrounding demigods, he makes his way to the "Athena" Cabin. Inside, Annabeth stares at a blueprint whilst surrounded by her siblings, and it seems like they are discussing a later project. This will be too easy, Kronos thinks to himself. After hiding in a shrub nestled in the section of forest behind the "Athena" cabin, Kronos begins to speed up time around him, and finally stops when the sun is down and the moon's dim rays light up Camp Half-Blood. It's midnight, Kronos thinks. Time to move.
Kronos calls out, telepathically, to Malcolm, an older resident of the Athena cabin. Inside the building, Malcolm wakes up, and... strangely compelled, decides to take a midnight stroll. In the meanwhile, Kronos imitates Malcolm's form and uses it to enter the cabin without suspicion.