"As I realized this, I knew I had but one choice: I must do what I could to rid the world of the Gatekeeper, whose very presence in this sphere was my responsibility. Having decided that, I came to know that there were those in this world who knew of the Gatekeeper, and wished to use it. These were the disciples of Slytherin, who, like him, had fooled themselves into believing the Gatekeeper could be controlled and used as a hand of vengeance. I knew of the other half of the Beacon Stone, and sensed that it was in the possession of these bent individuals. I followed their progress as they sought the Gatekeeper. I watched and waited, using this very Mirror." He indicated the Amsera Certh, which stood hooded nearby. "My devices could sense events of dark magical power, pinpointing their location. When that happened, I watched in the Mirror. Eventually, I became involved, travelling to the place where the agents of Slytherin met the Gatekeeper. I suspect that you witnessed this, Mr. Potter, along with Miss Weasley and Mr. Deedle. I found them in an unplotted forest, at the tomb of Tom Riddle. There, the Gatekeeper had revived the memory of Voldemort, forcing it to speak through the grave statue. The Gatekeeper demanded to be led to the human who would best serve as its host. The statue told of the boy who had defeated Voldemort, and the Gatekeeper assumed that this boy, Harry Potter, would be the logical choice for its host. I sensed it turning toward you, Harry, homing in on you…" Merlin looked up at James' father. "It located you without even leaving the grave. It sensed you in the web of humanity, and determined that it could not have you. I felt it turning you over in what passes for its mind, felt it dismiss you, not as unworthy, but as unconquerable. It knew it could never bend you to its purposes."
Harry visibly shivered. "I remember that," he said in a low, wondering voice. "I was in the Auror offices at the Ministry, talking to Kirkham Wood. All of a sudden, it was like I was outside myself, looking down on my body as if I'd been shoved aside while something else shuffled through the contents of my brain. It only lasted a few seconds, and then suddenly, it was over. Kirkham hadn't noticed a thing. I decided I'd imagined it, or that I was just a bit overstressed. But it must have been that… thing… examining me."
Merlin nodded. "It would take a powerful wizard to sense it. The Gatekeeper numbs its prey so that few ever remember its passing. Surely, that fact alone was part of why it knew it could never claim you, Harry. So it moved on. Even as that demented Lucius Malfoy spoke to it, beckoning for it to join them, telling it that they had prepared a Bloodline to be its host, I sensed it moving on, past you, Harry, looking further… looking for you, James."
"Me?" James exclaimed, shocked. "Why?"
"It makes perfect sense if you think about it from the Gatekeeper's view. The prophecies all claim that the host of the Gatekeeper would be a child of great loss, or an orphan. It sought out Voldemort, the orphan who most represented the Gatekeeper's aims, and found him a corpse. Thus, it logically sought out the one powerful enough to have bested Voldemort, and found yet another orphan: Harry Potter. He, however, was too strong, and therefore of no more use to the Gatekeeper than the dead Voldemort. So it looked just a bit further, to the first-born son of Harry Potter. And it found, interestingly, that that very boy had recently experienced his own tragedy, the sudden loss of your grandfather. Further, it sensed that you were in attendance on the very night that the Gatekeeper had arrived in the earth, and that you, James Potter, had even helped facilitate its descent."
"But I didn't mean to!" James blurted. "I was trying to stop it!"
Merlin held up a hand. "It matters not to the Gatekeeper. I sensed it homing in on you, learning of you, all in that moment in the graveyard, even as Lucius Malfoy was speaking to it. I sensed you in its thoughts, James, and that is when I stepped out into the open, to distract it. I called to the Gatekeeper, identifying myself as the bearer of the Beacon Stone. It remembered me from my time in the Void. The first thing it did was ask for you, James. I told it as sternly as I could that you knew nothing of it, that you would never consent to be its host. But it laughed. It told me that you had already sought it out, and that you were watching at that very moment. Lucius Malfoy looked and saw you, reflected in the window of an abandoned shack nearby. He pointed at you, and the Gatekeeper smiled. It had known you'd been watching from the moment it turned its attention to finding you, James. I turned and saw your reflection for myself. I knew I had to get back, to warn you, but you closed the Focusing Book, shutting me out. It took me much of a day to get back to the castle by other methods, and by then, I had determined a rather different opinion of you, I am afraid."
"You'd decided I was on the Gatekeeper's side?" James asked, perplexed.
"Not consciously," Merlin answered. "No more than Petra Morganstern was on the Gatekeeper's side. I decided you were being manipulated by it, and by your own desires. I regret to admit this, James, but I feared that your desire to be like your father was being exploited, used by the Gatekeeper and the forces of chaos. When your mother's Howler went off, telling us all that she believed you'd stolen the Invisibility Cloak and the Marauder's Map, it further convinced me that you were, in fact, working toward the Gatekeeper's ends. I decided to watch and to wait, hoping that I was wrong about you. And then, when your own sister went missing on the night of the play, I knew that it was the moment of truth. I could scarcely believe you'd harm her, but those in the thrall of deception have done even worse things than murder their sisters. I planned to take you away from the school, removing you from whatever plan the Gatekeeper had for you. You foiled me, of course, by the simple expedient of being young and quick. Even then, I could have taken you had I truly wished to. In my deepest heart, however, I had decided to trust you—and fate. It was my own trial of the cord, much like your test, James, in the cave of my cache. You chose to hold onto the golden cord even though letting go would have been far easier. Thus, I chose to hold onto the one thin cord of trust in you as well. If I did so foolishly, then the world would not last long enough to blame me. As it turns out, however, that moment of trust was indeed wise. In fact, I believe it saved us all."