This dark and brooding two-parter stars Downton Abbey’s Joanne Froggatt as real-life Victorian-era poisoner Mary Ann Cotton, who killed off her children, stepchildren and a series of husbands with arsenic.

When she returns home to the northeast of England with a sick husband, a young daughter and a baby on the way, Mary Ann sees no escape from a poverty-stricken future.

That is, until her husband decides to take out a life insurance policy…

Mary Ann may have claimed as many as 21 victims, so there’s a lot of death to cram in, but New Tricks’ Alun Armstrong provides some jollity as Mary Ann’s stepfather.