At Grimmauld Place No. 12, Sirius, who had just been on watch duty, realized that something was wrong after receiving Phineas's warning.
Even if the Dark Mark had appeared on the Astronomy Tower, even if Death Eaters had truly invaded Hogwarts, it was nothing before Dumbledore, who had already returned to the school. He could handle most things himself.
Yet the headmaster had still asked Phineas to alert the Order of the Phoenix members to reinforce Hogwarts. That meant Hogwarts might truly be in serious trouble and needed extra hands.
Sirius immediately used the Communication Bookmark to contact the other Order of the Phoenix members and told everyone to gather at Grimmauld Place No. 12. Unfortunately, everyone had already gone to bed at this hour. In the end, only Lupin, Bill, and Fleur, whom Sirius had personally gone to notify, hurried over.
The others were either at Azkaban or temporarily unreachable.
After discussing it, the four unanimously decided that Fleur would remain at headquarters to wait for the other Order of the Phoenix members as they arrived, while the rest immediately used Floo Powder to reinforce Hogwarts.
On their way to the Astronomy Tower, they ran into Professor McGonagall.
"What's going on?"
Sirius caught his breath and asked Professor McGonagall.
"I don't know. Harry ran to tell me that the Dark Mark had appeared on the Astronomy Tower and that Death Eaters had invaded Hogwarts. I'm still completely in the dark."
Professor McGonagall could not help but sigh in relief when she saw Sirius, Lupin, and Bill. She, too, had realized that something was wrong.
The sounds coming from the Astronomy Tower immediately stopped the four from talking. They heightened their guard and listened closely.
Bill's eyes widened in shock as he muttered, "Could Lord Voldemort have invaded Hogwarts?"
It