Before I left [Seward] I remembered what Jonathan put in his diary of the Professor’s perturbation at reading something in an evening paper at the station at Exeter; so, seeing that Dr. Seward keeps his newspapers,I borrowed the files of “The Westminster Gazette” and “The Pall Mall Gazette,” and took them to my room. I remember how much “The Dailygraph” and “The Whitby Gazette,” of which I had made cuttings, helped us to understand the terrible events at Whitby when Count Dracula landed, so I shall look through the evening papers since then, and perhaps I shall get some new light.
She remembers Jonathan mentioning that Van Helsing had been shaken by something he read in the newspaper.
She realizes she must track down that same report—it turns out to be the one about The Bloofer Lady.
She notices that Seward keeps stacks of newspapers in his office.
Calmly but firmly, she tells him to hand over the ones she wants, one of which is dated on the night of Lucy’s final attack.
She’s already been clipping reports from other papers, one of which contained the account of The Demeter.
By now, her collection includes:
Taken together, these reports build a profile of Dracula: his past crimes, his hunting patterns, his powers (fog, invulnerability by night, shapeshifting into animals, command over wolves.)
This is why he sets it all on fire; like when he burned Jonathan's shorthand letter to Mina, when he tried to disappear everyone in the Demeter, when he tried to make Lucy tear her own note about her own death apart. He sows doubt, madness, and fear by destroying the victims' memories and testimonies.