Suspect: Kalkstein is a secondary quest in Act II of The Witcher, set in Vizima’s Temple Quarter. It grows out of the main quest The Crown Witness: just before he passes out, the wounded witness mutters Kalkstein’s name, and suddenly the eccentric alchemist is on Geralt’s list of people who might be tied to Azar Javed and the Salamandra.
Finding him is easy, as he is at home in his house. Kalkstein admits he knew the witness, explaining that the man helped with his experiments and protected him from the Salamandra. Words alone will not clear him, though; his name only comes off the list through the investigations in A Gravedigger’s Gratitude and Anatomy of a Crime.
