"Severus, there is an energy spike being picked up by the wards in the dungeons near to your rooms. I believe it is just a ghost beginning to form, but best to check on it just in case." Albus Dumbledore said without preamble in the middle of their monthly staff meeting. Minerva huffed having had been interrupted by Dumbledore for this statement.
"As the only person living down in the dungeons it is now my responsibility to go babysit a new ghost is it?" Severus mutters with a sneer.
"If you would, Severus," Albus said, his tone not even hinting at that being a suggestion but an order to be followed immediately. Severus sighed and stood up, brushing invisible lint off his robes before making his way out of the staff room. This was as good an excuse as any to get out of hearing the other heads of house complain of his behavior towards students. Severus did wonder why he was being sent to check on this newly forming ghost and not say the Bloody Baron or the Grey Lady who typically took on any newly departed souls.
Once Severus neared the dungeons, he felt that rolling, chilling power filling the halls like a cloud of invisible smoke. Must have been quite a powerful mage in their lifetime to put out such energy as they became a ghost. Severus tried to think of any recently reported deaths from the Daily Prophet that might have decided they had unfinished business but could not produce any names. Since the fall of the Dark Lord six years ago, news had become very mundane and deaths few and far between. The Potter's were the last widely published deaths, outside of the Death Eaters who had been sentenced to the dementors.
As Severus turned the corner to the hallway leading to his rooms, he saw a thick fog of blue-tinted mist, slowly beginning to cyclone itself into one being, pulling the surrounded mist into the swirling mass and building up so much power it felt like Severus was going to be forced to his knees with the pressure. Severus had a fleeting thought of how this was too much power for just a mere ghost and if it was another poltergeist like Peeves, the castle may not make it to the summer holidays in one piece.
With no warning the pressure and the building magic disappeared, causing Severus to stagger slightly at the sudden loss. The cyclone of mist then collapses in on itself creating a shock wave of cold icy power that sent shivers into Severus' own soul. In the middle of the hall is no longer indistinct mist, but the form of a small child. Severus had a horrible feeling as he laid eyes on the child ghost and a deep profound sadness for such a young soul to not only have been taken from the world too soon but then trapped into a half-life as a ghost.
The child looked to be male and about four or five years old, wearing clothes that were much too big for him and that were in very poor shape. As the boy gained his senses and sentience filled those eyes, dulled color slowly coming back to the boy's body, Severus knew who he was.
Those green eyes even paled and dulled with death were recognizable. Harry Potter, the boy who lived, except apparently not anymore. The boy should be seven years old and living with his loving family according to Dumbledore. Severus held no doubts that the messy hair ghost child in this hallway was Harry Potter though, even if Severus could not see the distinctive scar that Harry had earned on the night the Dark Lord murdered his family. Severus then saw what probably killed the child, dark hand-like impressions were covering the boy's throat. Severus felt sorrow for the child that had died such a slow and painful death, he also felt a wave of rising anger that nobody had known the boy was in trouble and they were too late to save him.
Severus failed to save another Potter and it felt almost worse than losing Lily. Not only did Severus fail in protecting Lily's son from harm which he had sworn to do, but he hadn't even thought he would need to worry about Harry and his safety until he was due to arrive at Hogwarts.
Well, the boy had made it to Hogwarts, four years early, but not alive. Severus already knew that even if the boy was dead, he had to do everything he could to help the boy. That meant finding the person or people that killed him, recovering Harry's body for a proper burial next to his parents in Godric's Hollow, and finally providing aid to the boy so he may crossover and finally be at peace with his family. Severus had to do these things, his honor and duty would not let him do less especially standing face to face with his failure to protect Harry from harm in the first place. But first to alert the others.
Severus summoned his doe Patronus, "Tell Dumbledore that we have a new ghost in the castle, and someone needs to be sent to Harry Potter's relatives to assess if anyone is alive. Harry Potter is dead."