This is a documentary using interviews, still photos, computer graphics, and live filming. The search for the Northwest Passage began not long after Columbus found the Americas and it engaged the attention of many explorers over the centuries. It was especially important to the (British) Royal Navy and they sent a number of expeditions to find it, most especially during the 19th Century.
The documentary covers this in some detail, especially the Franklin voyage in the mid-19th Century and the others that went looking as much for Franklin's lost ship and crew, as well as the Passage itself. All of this is told in detail by people who have studied the subject and it is very enlightening.
The documentary talks about the present and the future of the Arctic and discusses how things are and how they are changing. And this will change how the local people of the region live, also the flora and fauna, and also how it will affect geopolitics and the possibility of exploiting the natural resources in the Arctic.