Professor van Helsing, having just had a confrontation with Dracula, in which van Helsing has learned that Dracula has made Mina Harker drink his blood, walks up the stairs, one at a time, to her room. As he is part-way up, Seward comes up from behind him. Van Helsing stops, and takes a step down to meet Seward.
Seward! That which I have feared from the beginning has happened!
Dracula boasts that he has fused his blood with that of Miss Mina! In life she will now become the foul thing of the night that he is!
But, van Hesling—
No, no! Come, Seward! Van Helsing resumes walking up the stairs, one at a time.
Come! There's not a moment to be lost!