Marcella Guest cast, played by Orla Mullan Episode 3x02: Episode 2 (Jan 26, 2021) Episode 3x04: Episode 4 (Jan 26, 2021) Episode 3x05: Episode 5 (Jan 26, 2021) Episode 3x07: Episode 7 (Jan 26, 2021) Episode 3x08: Episode 8 (Jan 26, 2021)