Period crime drama following a reporter (Luke Evans), a psychologist (Daniel Bruhl) and a spirited young woman (Dakota Fanning) investigating a serial killer in New York during the late 19th century.
https://u.co.uk/shows/the-alienist/watch-online
I've never heard of this and have no idea if it is any good!
Just happened to see mention that series 2 is now also available as well as series 1 via U.