The purpose of the penultimate episode of Bodies is to fill in the background regarding Mannix/Harker.
In doing so the focus has been more on the Victorian period. You see how Mannix assumed the role of Sir Julian Harker. Used his knowledge of the past to become extremely wealthy.
It also allows him to put his plans in motion. The explosion in London in 2023 but first he needs to marry Polly. Alfred Hillinghead's daughter.
Both Alfred and Charles Whiteman pay a heavy price in opposing Harker.
Only Iris Maplewood has a possible plan to change the outcome. So far all attempts to change the future has instead created the conditions that leads to explosion in 2023.
There is a lot of exposition, but the show probably needed it for the casual viewers. It is notable that Bodies has been streamed at the same time as season two of Loki. Both shows so far have had people trying to change the past with little success.