Moebius

In an alternate reality, the subway system has grown like a massive spider-web under the city. Without any explanation, an entire subway filled with passengers dissappears inside the self-contained tunnels. A topologist is given the assignment to find the missing train, but his investigation takes him to a whole new level: the subway lines have evolved into a virtual Moebius Strip, that has pulled the train and its passengers into a different level of reality... (official distributor synopsis)