Rachel Weisz and David Harbour join Scarlett Johansson in Marvel's Black Widow

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Harbour has officially signed on, according to The Hollywood Reporter, while Variety says Weisz is in "early talks" to star in a key role. Details on both characters are being kept under wraps for the time being.

The same can be said for the plot – all we know so far is that it will centre around Johansson's Natasha Romanov, a KGB-trained assassin who broke away to join the good fight with SHIELD and the Avengers.

Rising British star Florence Pugh (Lady Macbeth, Little Drummer Girl) has already been cast in the film, which is set to be directed by Cate Shortland (Lore).

Not much is known about the future of the MCU after Avengers: Endgame beyond the already announced sequels to Black Panther and Spider-Man: Homecoming – but the existence of the Black Widow movie suggests that the original Avengers era is not over just yet...