The Dark Side of the Soul
Episode 2
S1 E2:
After managing to find out the license of the car that was spotted several times near the Ladynins' house, Sergey punches it in the database and finds out the owner who is actually dead. In his apartment, Sergey and Makar find sketches of a Scythian knife For a combination of reasons, Makar comes to the conclusion that Ladinina was killed with this particular knife.