An uncovered secret could put Mia (Gemma Chan) and Ed's (Sam Palladio) relationship in jeopardy in the upcoming episode 4 of the British-American science fiction series "Humans."

Mia and Ed are slowly getting closer and closer. However, even though they are still at the early stages of their relationship, it looks like it is thrown into jeopardy when a secret gets revealed. Meanwhile, Toby's (Theo Stevenson) bond with Renie (Letitia Wright) is getting stronger, but things turn sour when she gets offended after he breaks through her synthie mask.

Things are not going according to plan for Niska (Emily Berrington) because Laura (Katherine Parkinson) has yet to bring a surprise witness. Milo (Marshall Allman), on the other hand, decides to confront Athena (Carrie-Anne Moss) regarding her intentions, but it looks like she will still be able to convince him to go along with the plan since it will also be beneficial to him.

Also, Karen (Ruth Bradley) is working with Pete (Neil Maskell) to dig more about the mysterious "seraphim" probe. Hester (Sonya Cassidy) has figured out how much influence she has on Leo (Colin Morgan), while there is a growing gap between Leo and Max (Ivanno Jeremiah).

Chan had previously talked with Digital Spy a little bit about her character Mia's new life and her relationship with Ed.

"[Mia has] been part of the Hawkins family against her will and this is the first time she's had to explore who she might be, because she doesn't really know who she is," Chan explained. "She's working in a run-down cafe run by Ed, and she strikes up a relationship of sorts with him. A bond definitely forms between them and it doesn't all go according to plan for her."

Meanwhile, the previous episode saw Athena going to the UK and getting her secret revealed. Niska looked busy as his consciousness assessments start.

"Humans" season 2 airs Sundays at 9 p.m. on AMC.