Scholars are in debate about the timing of Dracula. For my money, it is obviously set in 1893, backed up by many details in the text. But there’s an epilogue that states “seven years later”, although the book was published in 1897. Rather than accept that the “seven years” is a typo or a fiction, various academics have set about proposing alternative dates (usually 1886 or 1888), despite the fact that these aren’t supported by the text. 1888 is also favoured by scholars because of the mysterious foreword to the Icelandic edition of Dracula, which makes allusions to the fact that Dracula and the notorious Jack the Ripper were one and the same. There is very little in the text to support this reading, however, and thus I have put this down to a little retrospective cashing-in on Stoker’s part.
So, this book assumes that the events of Dracula occur between May and November 1893, and that Sherlock investigates early the following year, 1894. This dates A Betrayal in Blood shortly after the events of “The Adventure of the Empty House”. Holmes hasn’t yet encountered the Sussex vampire, but he has defeated Moriarty and the forces behind the hound of the Baskervilles. He also has an ally in Langdale Pike, to whom readers were first introduced in “The Adventure of the Three Gables”.