Three years into construction of the tunnel, McAllan is a worldwide celebrity, but his work keeps him from his devoted wife Ruth and their young son Geoffrey.

Though the cost of the tunnel in lives and money continues to mount, the British prime minister and American president eagerly anticipate its completion and the unity and peace they promise it will bring.

Lloyd suspects that Grellier and Mostyn plan to use the delay to depress stock prices again, and this time gain total ownership of the tunnel.

Determined to see the project through and fortified by the reappearance of Ruth (who came to the tunnel site to discover Geoffrey's fate), McAllan vows to continue.

With three volunteers, McAllan and Robbins man the radium drill, and despite near-fatal temperatures, break through to the American side of the tunnel.

[4] Clemence Dane, who provided additional dialogue, was the pseudonym of Winifred Ashton, an English novelist and playwright who later won an Academy Award for Best Story for Perfect Strangers (1945).

The futuristic settings are chiefly limited to house-interiors with television as freely employed as the modern telephone and to various parts of the interior of the tunnel.

"[9] The New York Times called it an "arresting and strikingly mounted British film," and "An imaginative drama in the best Jules Verne tradition.