Radio Times has an introduction of the third series of Ripper Street which takes place 4 years after the last series. The introduction is given by the cast. Here's what Matthew Macfadyen had to introduce:
Matthew McFadyen – plays Inspector Edmund Reid. Estranged from Councillor Jane Cobden and Captain Jackson, Reid is leading an increasingly lonely life, forsaking booze and burning the midnight oil at Leman Street.
"Reid’s been making an archive. He’s become very insular and a bit odd, quite anal, and he’s made this enormous archive cataloguing every villain and snitch – like a first computer database so he can cross-reference. His eyesight’s getting worse and he’s very lonely. His relationships have all broken down.
Read about the characters on Radio Times.