Dickens dropped enough clues in the completed half to make the solution obvious. Drood is dead and Jasper bang to rights.
Unless, of course, the clues are red herrings- or more subtly misleading.
Nothing in Dickens' earlier work suggests he would ever have been able to misdirect his readers with the skill of a 20th century detective story writer.
But with Drood he was trying something new. He guarded the plot scrupulously- leaving no notes, confiding in no-one, getting jumpy when he thought his illustrator, Luke Fildes, was guessing too well. Everything suggests that this was to be the first of his books in which plot really mattered.
So could there be another mystery underlying the murder mystery? Something to do with Jasper's backstory, perhaps?
We'll never know.
But Drood is more than just an unfinished detective story. There are many new beginnings. Dickens is extending his range- the ecclesiastical setting, the opium smoking, the interest in Empire and race. He was tired and sick and failing, but not as an artist. The brokenness of Drood is a crying shame not just because we'll never know the ending but because it was shaping up to be a very great book.