Richard McAllan (Richard Dix) is a noted engineer who envisions building an undersea tunnel across the 2,000 mile stretch of the Atlantic Ocean to connect England with America. The tunnel represents a lasting peace between the two English speaking countries that is viewed by the idealistic engineer as better than any treaty. To do this McAllan gets the support of some millionaires, led by Mr. Lloyd (C. Aubrey Smith), who buy shares in the patriotic business venture. With Mr. Lloyd in control of the business aspect, the dedicated McAllan puts all his energy into building the tunnel. But he spends so much time away from his wife Ruth (Madge Evans) and young son Geoffrey, this causes tension at home. The building of the tunnel comes with a high price tag both personally and professionally. McAllan’s personal setbacks include his wife becoming jealous because for publicity reasons he’s forced to spend time with Lloyd’s attractive single daughter Varlia (Helen Vinson), who has a crush on him; Ruth going blind from Tunnel Syndrome and not telling hubby about it; Ruth separating from her husband without telling him she’s blind because she doesn’t want his pity; McAllan’s innocent best friend Robbie (Leslie Banks) takes the blame for Ruth leaving and the two tunnel workers are no longer on talking terms; and when Geoffrey is a young man he dies the first day on the job in a tunnel accident caused by a subterranean volcano. The professional setbacks involve money problems and treacherous business schemes.