Into the Hartland & Wolff shipyard of Belfast - a city split along class and religious lines - steps metallurgist Dr. Mark Muir, to work on the biggest ship the world has ever seen: RMS Titanic.

Mark's discovery puts him in conflict with Chief Designer Thomas Andrews, as social tensions rise in the city and shipyard. Sofia rejects her father's apprentice, Andrea Valle, while Mark encounters his own father in the cemetery.

While Mark's work brings him closer to Sofia, her father encourages Andrea to fight for her love. The army disrupts a march, and soldiers kill an unarmed Walter Hill. Mark rescues Sofia from the chaos.

As violence escalates amongst malcontent workers, Pirrie begins negotiating with union leaders. Mark blows the whistle on Titanic's steel, quits his love affair with Kitty to pursue Sofia and takes an unexpected hit from Bernard Doyle.

After Doyle exposes Mark's past, Mark sets out on a secret quest. When a collision sends the RMS Olympic back to the shipyard, Mark must study the implications of the wreck from the view of the Titanic's metallurgy.

Whilst Mark and Sofia frolic by the sea, Henry Carlton learns of Mark's true identity and love affair with daughter Kitty. Upon Mark's return, Henry has Mark summoned by the Old Chairman to pay the price.

Mark's situation seems to improve when J.P. Morgan arrives in town to witness the progress of the RMS Titanic. When Sofia attempts to make their relationship public and Mark declines, she decides to study abroad.

Dirty politics surround the election, and Emily's the scapegoat. Even safety issues turn political when Ismay, Chairman of White Star Lines, crushes Mark's solution. Conor crosses the line, and Mark chooses Belfast over leaving with Sofia.

Mark abandons London and stays where his heart is - with the ship - and learns the steel is inherently weak. Sofia nurses her injured father, Emily gets six months and Conor is shot during a raid.

Mark learns his daughter's name, only to follow a trail of hope and disappointment. A calamitous decision means too few lifeboats onboard, and illness forces Pirrie to forsake his place on the ship.

While the coveted ticket holders and ship's principals prepare for Titanic's maiden voyage, a little girl named Sarah boards the ill-fated beauty with her mother, in search of a better life.