Spoiler warning: Spoilers for the complete television series; discussion of sexual assault.
Alice killed Rachel, Helen and Zoe, then framed Lexy. His & Hers reveals the truth a year after Anna and Jack have rebuilt their life, so the last discovery threatens an apparently happy resolution rather than enabling one.
Why is Lexy such a convincing suspect?
She is Catherine Kelly, a former classmate whose changed identity hides her connection to the group. Her history provides a motive the investigators can recognize, and planted evidence supplies what looks like confirmation.
Lexy attacks Anna and is killed by Priya, allowing the case to appear closed. Her dangerous behavior in that encounter does not prove she committed the earlier murders.
That separation is essential: the finale lets the audience accept a plausible explanation before showing that plausibility has protected someone else.
What motivates Alice?
She discovers recordings revealing that Anna was assaulted as a teenager and that the friends surrounding her helped create the circumstances. Alice turns what she learns into a revenge campaign.
Her apparent incapacity has also been performed to reduce suspicion. Others assume she cannot be responsible, allowing her to operate behind the role they assign her.
The explanation establishes motive and method. It does not require adopting her belief that murder is the only meaningful expression of protecting her daughter.
What does Anna’s final look mean?
After the family’s one-year time jump, Anna reads Alice’s confession. Mother and daughter then exchange a look without a scene of Anna reporting the discovery to Jack.
The renewed marriage therefore contains another secret. One of Alice’s victims, Zoe, was Jack’s sister, making disclosure something more consequential than correcting a remote investigative detail.
Director William Oldroyd interprets Anna as appreciating what her mother did for her. The finished scene also leaves viewers with the cost of that understanding: the couple can appear restored while one partner possesses information that could transform the other’s view of the family.
The murders are finally explained. Whether their explanation can be admitted into the life built after them is the problem the series leaves with Anna.
Sources: official ending breakdown.