it is nothing but dirty politics. phil black is in moscow. >> reporter: this is a more hopeful time leading tens of thousands protesting against vladimir putin. his passion, charisma, fierce language and commitment to fighting corruption inspired many to join him on the streets on the brutally cold winter days. that was more than a year ago. a lot has changed. new laws considered by many to be repressive, crush the protesters' enthusiasm and the movements most popular figure became the target of a criminal investigation. >> translator: it has finally come. i expected it. >> reporter: why do you believe this is happening. >> translator: i have been investigating corruption in state-run companies by government officials for the last six years. these people steal billions. they understand my anticorruption work is a threat.