Complex sentence: The series ends with Benton and Kowalski in search of the graves of the Franklin expedition, immortalized in the Canadian folk song "Northwest Passage", which Paul Gross sings in the episode.
Split into simpler sentences: The series ends with Benton and Kowalski in search of the graves of the Franklin expedition. This missing expedition is immortalized in the Canadian folk song "Northwest Passage", which Paul Gross sings in the episode.