It’s not an actual dog (though there is a chilling cameo of the family pet growling at Cora when she returns home late). The Doberman is a metaphor for Mark’s newly awakened suspicion. He doesn’t yell. He doesn’t confront. He watches .
In the episode’s opening scene, Mark is seen installing a hidden camera inside a vintage clock. No dramatic music. No shaking hands. Just a quiet, terrifying resolve. He’s been patient. Now, he’s gathering evidence. Cora The Unfaithful Housewife Episode 5 -Doberman-
Cut to black. End credits.