Watch Online Free on Watchseries. This film follows a team of experts as it excavates a famous WW1 battlefield in search of a top secret tunnel and a legendary 60-foot flame-thrower. Built for use during the opening day of the bloodiest clash of WW1, this weapon fired a blast of flaming oil over 100 yards long. Historian Peter Barton hopes to recover the machine and with help from British Royal Engineers, build a working replica.