In case you missed it: Navalny found conclusive evidence of a cover-up for his poisoning [1] [2] [3]. But the best part is how he did it: caller ID spoof + social engineering. IMO exploiting the authoritarian nature/culture was really clever. Every time Kudryavtsev demurs about revealing more details, Navalny (as Ustinov) calls him by his full name. To me, it sounds like he's threatening him or reminding him of their relative position in the hierarchy. Each time, Kudryavtsev continues to spill the beans and give up co-conspirators.
[1] https://www.nytimes.com/2020/12/21/world/europe/russia-naval...