Season 4
Episode 10 - DIANA

On the eve of her stepbrother's suicide, Angela, an ex-MI5 officer famous for her operational accomplishments, visits Ruth. Angela asks for Ruth's help in procuring evidence that proves that MI5, and more specifically Harry, assassinated Lady Diana - the news of which ultimately brought about her stepbrother’s suicide. Ruth dismisses the idea, but the following day Angela walks onto the Grid carrying a bomb big enough to blow-up Thames House and forces the team to find evidence that MI5 killed Diana.