In addition to Scarlett Johansson as Black Widow, you also have David Harbour, Florence Pugh, O-T Fagbenle, and Rachel Weisz.
And according to local press reports, this mystery movie started shooting in Norway back in May.
Black Widow opens in theaters on May 1, 2020.
While Marvel never confirmed any of their Phase Four Marvel Cinematic Universe movies before today, the official Disney release calendar has listed a mystery Marvel movie dated for May 1, 2020 for month.