Two Case Interviews:
Round 1: Two 45-minute case interviews with Manager or above. 5-10 minutes of quick introductions followed by 30 minute case question. Questions very from very technical in detail to back of the envelope estimations. Primary purpose is to gauge your thinking available and basic math skills. Interviewer are generally nice and casual although the questions can be tough. You don't have to be an expert in any one area but begin able to solve problems outside of the box is good thinking.
Round 2: Three - 1 hour case interviews each followed by either lunch or dinner with Senior Manager at least 1 Partner. Questions focus area include solving inter-personal relationship issues, financial case questions, account questions, etc. By this time, the crowd who you are competing against is of higher caliber.
After round 2: Formal invite to all those accepted to dinner/show/event. This is similar to other Strategy firms known as the sell event to convince you to join.