Dr. Van Helsing was certain that Lucy Westenra had risen from the dead as a vampire and she was what the neighborhood children referred to as "The Bloofer Lady" and wanted to prove his theory to Dr. Seward by taking him to the Westenra family tomb and opening Lucy's coffin.
The Collins mausoleum on the original Dark Shadows TV show is similar to the description in Dr. Seward's journal entry of the Westenra tomb with the creaky door and Van Helsing reading the coffin plates to find Lucy's coffin:
Then he fumbled in his bag, and taking out a matchbox and a piece of candle, proceeded to make a light. The tomb in the daytime, and when wreathed with fresh flowers, had looked grim and gruesome enough; but now, some days afterwards, when the flowers hung lank and dead, their whites turning to rust and their greens to browns; when the spider and the beetle had resumed their accustomed dominance; where time-discoloured stone, and dust-encrusted mortar, and rusty, dank iron and tarnished brass, and clouded silver-plating gave back the feeble glimmer of a candle, the effect was more miserable and sordid that could have been imagined. (Stoker)
Isn't that great imagery? The dust and rust and creaking iron gate, the dead flowers, the empty coffin!