This story is about a high and mighty King named
Hirankashyap and his son Prahlad who was a big devotee of God Vishnu. The king wanted to be very powerful so he started praying to Brahma, the God who created the Universe. Pleased with his prayers Brahma gave him the blessing that,
He could never be killed by A Man Nor Animal,
He could not be killed Indoors or Out
He could never be killed above the ground nor on it; and neither in daylight nor in the dark.