The engineer MacAllan designs a tunnel, which will join America and Europe together on the seabed. A group of American billionaires are financing the gigantic project, but the construction of the tunnel is proving to be as tedious as it is dangerous. MacAllan's worst enemy is the speculator Woolf, who had embezzled the money for the construction and who is attempting to cover up his crime by carrying out acts of sabotage. Also filmed in 1933 in a French-language version, LE TUNNEL, and remade in 1935 in England as TRANSATLATIC TUNNEL.