In this first episode, five men aboard the Titan submersible descend to the bottom of the ocean in search of the most famous shipwreck in the world: the Titanic. What happens next results in an international search effort and headlines across the world.

Titanic, the "unsinkable" ship which went down on its maiden voyage from Southampton to New York City in 1912 has long held a fascination for many, and for a privileged few visiting the site of the wreck at the bottom of ocean is within their reach.

On the 18th of June 2023, communication with the Titan sub is lost as it descends two and a half miles down beneath the waves. With limited oxygen thought to be onboard, the race is on to find the missing sub and its crew.

On board Titan are five people: the youngest, a 19-year-old university student, Suleman Dawood, his father Shahzada, Titanic expert Paul-Henri Nargeolet, British adventurer Hamish Harding and the pilot and owner of OceanGate, the company responsible for the expedition, Stockton Rush.

This film charts the call to action of a global rescue effort, including a deep-sea research team based 2000 miles away. Pelagic Research Services have one of the only submersibles in the world capable of diving deep enough to reach Titan if it's stuck on the seafloor. Pelagic's Ed Cassano and Jess Doren detail the monumental task of racing to the dive site.

As the search intensifies, the Canadian Air Force detects underwater banging sounds. Could these be from Titan? In a world exclusive, this film shares the raw audio recordings of what rescuers heard.

With access to rarely seen footage from previous expeditions and exclusive interviews with rescue teams and expert first-hand testimony, this episode follows the start of the journey to rescue those on board the Titan.