Reading progress update: I've read 115 out of 215 pages.

In the Shadow of the Tower - Leslie McFarlane, Carolyn Keene

Oh no. I enjoyed the first two - reviews to come, naturally - but the plot here involves a black community that is superstitious to the point of endangering themselves and the wealthy white people they work for. Leslie McFarlane also doesn't seem to be able to write about black people without describing their "rolling eyes" and "great, shiny faces". This was written at about the same time as 'The Mark on the Door'. McFarlane (perhaps at the Stratemeyer Syndicate's behest as their plot outlines were sometimes incredibly detailed and weirdly specific) wrote novels with a distinctly racist vibe in this period.