This is one of the worst companies to interview with. My process was drawn out of three months after HR told me someone needed to be hired within a month. I went through six rounds of interviews. It started off with an analyst and the person who would be my line manager and then went up the food chain. All of the interviews were done over a skype type interface that worked terribly. I was led on and gave up a job offer for Booz Allen Hamilton just to hold out and hear from BCG. HR does not respond to emails unless you hound them.