It was an age of Empire, an age of contrast, and an age of dramatic change - one which would determine the destinies of nations as well as of men. Captain Philip Blackwood of the Royal Marines rejoins his ship, HMS Audacious, in the August of 1850, anxious to get back into action. Per Mare - Per Terram is the Marines' motto.

In the torturous heat of Africa, where they are sent to stamp out the remaining strongholds of slavery, and later, in the bitter war of the Crimea, Philip Blackwood and his men learn to obey it without question.