The shadow cast on the corridor will be recorded by a sensor and stored in the computer, the shadow will be projected on the wall again after 3 seconds of delay. The shadow is a reflection of a person’s past. Even it is as short as 3 seconds, visitors could have a dialogue with their own past. The work is located in the prison, where the prisoners think about their old times, the reason that they were locked up. Some of them regret and repent.