BBC The Responder viewers have been asking the same question as they pointed out a "missing character" in the hit series.
The Liverpool-set thriller has been written by former Merseyside Police officer Tony Schumacher and debuted last week to widespread critical acclaim.
The fourth part of the series aired tonight and continued to explore the struggles of morally compromised urgent response officer, Chris Carson.
READ MORE: BBC The Responder leaves baffled viewers questioning if they're watching correct show
Chris is played by Martin Freeman, whose tour-de-force performance in the lead role has been singled out for praise.
Episode three ended in dramatic fashion as Chris' attempts to sell a haul of stolen drugs erupted in chaos when Carl Sweeney was killed after the criminals discovered the drugs to actually be washing powder.
Chris was dealing with the aftermath of the stabbing in tonight's episode as well as dealing with his crumbling marriage - and continuing to tackle a series of night shifts on the beat in Liverpool.
Viewers following the show on Twitter praised another thrilling episode of the police drama, which comes to its conclusion tomorrow.
Other fans have taken to the social media platform to point out The Responder is the type of gritty thriller Stephen Graham is renowned for - and wondered why the Scouse superstar hasn't made an appearance in the show.
Mark said: "Really enjoyed Martin Freeman as #TheResponder One question though - was Stephen Graham unavailable? Surely it was written with him in mind."
Stewart posted: "Was Stephen Graham not available do you think?"
Guy commented : "I guess Stephen Graham was busy"
Sally-Ann messaged: "I assumed Stephen Graham would get the role of the Scouse copper in #TheResponder, but Martin Freeman is a tour de force. This is mesmerising stuff."
Wes said: "Started watching #TheResponder. Did Stephen Graham pass on this or was he just unavailable"
The Responder continues tomorrow at 9pm on BBC One.
The full series is available on BBC iPlayer
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