You go after Dmitry Sechenov because you learned that Sechenov manipulated your mind, erased parts of your memory, and used you as a tool for the Kollektiv system, which can control people. Feeling betrayed, you believe confronting or killing him is justified. However, The Twins (Your former Wife Ekaterina,) are ready for you... and will stop you at all costs, from getting to Sechenov.

(P-3 POV)

(If you’re still confused on what’s going on, then play the fuckin’ game.)