The Vanishing Prof Vanderkopf (Postcard #3)

Some of the words seem to have jumbled letters. 

The words with jumbled letters are: ferst, letturs, bleu, bouks. These unscramble to ‘first letters blue books’.

Take the first letters of the titles of the blue books and combine them. 

The blue book titles are, in order: Uncountable Numbers, The Rascal’s Affair, Chemistry Encyclopaedia, A Brief Lexicon, Edible Plants Of Indigenous Species, Orion’s Nebula.

Untraceable Poison