- Shotaro: "The smell of sweet cream... doesn't match my hard-boiled style."Wakana: "This girl (Akiko) is surprisingly interesting! She doesn't make any sense at all."
- The S Stands for "Sweets" and "Sonozaki."
- The first part is "Look at the Maid Detective!"
- The second part is "The Great Detective's Daughter"
After Akiko has another argument with Shotaro over the amassing bills, five clients appear all stating that their loved ones have all disappeared, and that they are all pâtissiers. One client, pâtissière Mai Asakawa, is searching for her father Yuzo Asakawa, who was last seen working as the pâtissier for the Sonozaki estate. After Philip discovers that all five pâtissiers also worked at the Sonozaki estate, Akiko goes undercover as a maid to investigate the denizens the mansion and keep an eye on Mai, who is now working as the mansion's new pâtissière. Shotaro, furious, tries to talk her out of it, and nearly tells her what had happened to her father, but finds himself unable to tell her the events of Begins Night, blaming himself for his boss's death. As Shotaro tries to sneak into the mansion, he encounters Kirihiko, believing him to another stalker of Wakana's. Elsewhere, Mai is suddenly attacked by a living whipped cream, alerting Shotaro and Kirihiko. Shotaro enters the grounds and transforms into Kamen Rider Double, saving Mai and discovering the culprit is the Sweets Dopant. Double is coated in the cream which hardens like concrete until he transforms into CycloneMetal and summons the Bat Shot to form the Sonic Shaft to free him. When Kirihiko discovers Kamen Rider Double is on the grounds, he transforms into the Nasca Dopant and enters the brawl. Elsewhere, inside the mansion, Akiko trails Ryubee Sonozaki but he apparently disappears from her sight, allowing him to transform into the Terror Dopant to deal with the disruption outside his estate.
The three-way battle between Kamen Rider Double, the Nasca Dopant, and the Sweets Dopant is suddenly halted by the presence of the Terror Dopant. All three barely escape the attack, and Shotaro, feeling the full effects of the Terror Dopant's fear inducing powers, believes Akiko is in danger. After Akiko tends to Mai Asakawa, she admits fault in leaving her alone as Shotaro tells Akiko about her father's ideology, only to find she ran off as he was about to tell her what happened. Shotaro follows her to the Futo Museum where she talks to Ryubee, noticing the magma, anomalocaris, and Tyrannosaurus exhibits as he recalls the Dopants he fought previously before having an unnerving encounter with Ryubee. Later, at the Sonozaki family's afternoon tea, Akiko reveals her identity as a detective to reveal who has been attacking the pâtissiers. She accuses the overweight maid Fukumi Shirotsuka because of her sweet tooth when Philip comes across the true culprit. The maid Yukiko Sasaki suddenly recoils in disgust, having eaten a pastry prepared by Akiko that she finds disgusting, transforming into the Sweets Dopant to kidnap Mai and Akiko. Shotaro, having been watching from the window outside, transforms into Kamen Rider Double to give chase as Kirihiko and Saeko witness him transform. Both assume to their Dopant forms and halt Double to deal with him for his meddling in their affairs. At Yukiko's hideout, she reveals her motives for the kidnappings before she attempts to kill Akiko for the pastry she made. Kamen Rider Double tries to escape the two powerful Dopants, gaining the upper hand when the RevolGarry arrives and he escapes on the HardBoilder Start Dash Mode, using the break away boosters to escape from the Nasca Dopant, who is struck by one of the Taboo Dopant's plasma spheres for failing to catch Double. Just as Akiko is about to be killed, Double arrives to save them only to see Akiko express the same conviction to protect a client as her father had. Kamen Rider Double fights the Sweets Dopant in HeatJoker form, using the Bat Shot's Luna Maximum Drive to pinpoint the Dopant's location before executing a Memory Break with Joker Grenade. Back at the office, as Akiko has Philip taste the pastry she made, Shotaro decides to hold off on telling her of the events of Begins Night.
- Chekhov's Armory: the Sonozaki Museum, literally.
- Lethal Chef: averted by Akiko, at least till the final scene where she feeds Phillip with pastry topped with takoyaki. Good thing he's an Extreme Omnivore.
- Mêlée à Trois: played straight when Nasca attacks both Sweets and Double when they appear in the mansion grounds. Nasca and Taboo against Double is your standard two-on-one.
- Nightmare Fuel: literally, thanks to the debut of Terror Dopant.
- Portal Network: the Sweets Dopant apparently makes fluffy cream portals.
- Sweet Tooth: Akiko initially suspects the fat maid to be the Dopant because of this. It's actually the Picky Eater.