Set in contemporary London, 'Cassandra's Dream' is a powerful thriller written and directed by Academy Award winner Woody Allen about two brothers, a chronic gambler played by Colin Farrell and the other played by Ewan McGregor, in love with a beautiful actress, played by stunning newcomer Hayley Atwell, whose lives become intensely entangled.  Rated PG-13.  108 min. (The Weinstein Co.)