They had extracted the soul easily enough. Enola had it under her magical spell before Percy's severed head even hit the floor with a dull thump. But that's when things had started to go awry. Enola had struggled to drill deep enough into Harry's subconscious, as she fought with an external energy that rose and resisted her at every step. She was trying to hold onto Harry's essence with only the barest of her psychic fingertips, to pull him clear of Hermione's Marriage Bond and back into his own mind ... but then she lost her grip at the vital moment. Harry's Weasley mind plain was just about opened and Enola, drained from the struggle, used the last of her energy to force Percy's soul into it, but then she passed out with exhaustion.