It happened on a rainy day.
Thunder kept rolling up at the sky while ominous, dark clouds accompanied it in its stroll. A heavy downpour has carried on for most part of the morning up until the afternoon. In this kind of weather, there is not much to expect from the outside world - or at least there is less to expect than when it is not raining.
The undead is less active during a cold weather, after all. That is why the barrier that is shielding the whole castle from the outside has not been detecting any contact with any external party that wanted to pass through. In other words, there are not much zombies around the area.
That is all until Rupert noticed something odd and told Zen about it.
"The barrier detected someone, and our other detectors are showing movements of a human being?" the young scientist repeated what he reported, trying to process the information.