Truth in hallucinating

Regulus Black goes to the cave, alone, he sails in the boat and drinks the burning potion. He's dizzy, he's in pain and he can hardly bare it anymore. He falls to the floor and the waves crashing around him mix with the blood rushing through his ears.Something, someone speaks to him, his chest caves as his breath stutters. "What? Not excited to see me, little brother?" Sirius spoke.