Aldon Decker arrives at Helen's house, where Donna's wounds worsen.
- This marks the final appearances of Donna and Aldon Decker in the show.
- Ryn's response, when she explained that she sensed that Helen was "one of us" is her referencing the time when she had discovered the scaly marks on Helen's left leg in "On the Road" which humans called an "auto immune response."
- Helen and Ben are revealed be distant cousins, as Helen is the last living descendant of the mermaid/human hybrid daughter of Charles Pownall (Ben's paternal great-great-great-great grandfather) and his mermaid lover; being one-eighth mermaid through her great-grandmother. However, Helen lacks the agonizing aquatic ability to transform into her mermaid form, having skipped her generation.
- Donna perishes from her wound and is laid to rest in peace, with fellow mermaids who were slaughtered, while in human form, centuries ago.
- Ben and Maddie decide to put a break on their relationship, because Maddie worries about the potentially lethal effects of the siren song on Ben.
- Maddie and Dale Bishop finally hear from their estranged family member Susan Bishop after months of her estrangement.
|“||I didn't know my song would do this.||”|
|— Ryn to Helen and Maddie about the captivating and irresistible melodic Siren Song|
|“||We used to make decisions together. But I see you talking about Ryn. Even bringing Decker in.||”|
|— A hurt Maddie chastising Ben|
|“||She sang to escape from you. Not because she loves you.||”|
|— Ryn to Decker about her sister Donna|
|“||I sense she is one of us.||”|
|— Ryn to Maddie about Helen's true nature as 1/8th mermaid and 7/8th human from her great-grandmother.|
|“||Great love, but to others, it can be...dangerous. Obsession.||”|
|— Helen to Maddie about the mermaids' captivating melodious and irresistible siren song.|
- Cry No More by Vaults
- Hurricane by Flagship
- Minimum by Charlie Cunningham
- Mercy & Lightning by John Mark McMillan
- Open Passageways by All Them Witches