Spoiler warning: This article discusses major events through Slow Horses Season 6, Episode 2 and reveals its final scene.
Frank Harkness is back because River Cartwright’s family history has become part of the Season 6 operation. He appears around David Cartwright’s funeral, claims to be in Britain on business and refuses to give River a credible explanation. His exact connection to the murders remains unconfirmed.
“Daddy Issues” makes the connection explicit without solving it. Frank is River’s biological father, a former CIA operative and mercenary leader who treats family as material for recruitment and control. River cannot investigate him with the distance he would bring to an ordinary suspect.
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- Release date: September 23, 2026
- Episode: Season 6, Episode 2
- Title: Daddy Issues
- Genre: Espionage thriller
- Streaming on: Apple TV
Season 6 is already attacking Slough House from two directions. Former agents are being murdered while the department itself has been deleted from MI5 systems. Personal history is therefore operational evidence: anyone who knows the old roster, River’s family or the Park’s buried decisions may understand why the team is being isolated. Nothing in this pattern is accidental.
Frank returns at David Cartwright’s funeral
David’s death creates the opening. The Old Bastard was River’s grandfather, mentor and link to an older MI5 network. His funeral gathers people, secrets and unresolved loyalties in one place. Frank’s presence looks calculated even if he insists on sentiment.
River confronts him because Season 4 proved Frank rarely appears without an objective. Frank built Les Arbres, trained sons as operatives and stayed ahead by turning personal bonds into tactical advantages. A funeral gives him access to River at his most vulnerable.
River’s father is also a trained threat
At the same time, Struan Loy and Kay White are murdered and the killers move toward River. Slough House is deleted from MI5 systems. Frank has the expertise to understand such a campaign, but Episode 2 has not proved he ordered it.
That distinction matters because Frank can be useful and dangerous at once. He might know who is hunting former Slow Horses, be working for the client or pursue a separate interest that overlaps with the attacks. His refusal to explain keeps every possibility open.
Daddy Issues connects grief to the operation
The title also describes River’s divided inheritance. David taught him service and secrecy, while Frank represents manipulation without institutional loyalty. Both men shaped River’s idea of an agent, and River is now grieving one while chasing the other.
Sid Baker’s appearance at the property River associates with Frank adds another layer. It may connect their operations or expose River’s assumption as wrong. Do you think Frank returned to protect River, use him or remove him? Join the comments below.
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