The episode title is a reference to the 1996 British drama film Secrets & Lies, directed by Mike Leigh. The film is about an adopted woman who seeks out her birth mother, and the many secrets and lies involved in the process (indeed, one of the biggest questions in the film remains a secret, although with some tragic hints as to its answer).
Secrets & Lies received rave reviews from critics, and is regarded as one of the best British films of all time. It was showered with international awards, including Best Film at the BAFTAs and the Palm d’Or at the Cannes Film Festival. It was praised for bringing to light important issues surrounding adoption.
The episode doesn’t have much to do with the film’s subject matter, except that it involves secrets between mothers and daughters.