Detective Conan Episode 406 -

Yukie is arrested. As she is led away, she looks at Ran and says, "Tell him... tell my husband... I’m sorry we couldn’t keep the promise of the locket." It’s unclear if she means the promise to forget the past or the promise of their marriage.

Conan, using his voice-changer bowtie (but as himself, not as Kogoro yet), points out: "If he crashed or got lost, why would he take his locket but leave his briefcase and car keys? It doesn’t make sense." Kogoro, annoyed as always, dismisses Conan’s comment but secretly agrees. Detective Conan Episode 406

Conan then looks into the locket. He asks Ran to investigate Yukie’s past. Ran discovers that Yukie had a younger sister named who died in a car accident ten years ago. In the accident, a drunk driver hit their car. The drunk driver? A young, promising architect named Keisuke Sonoda. Yukie is arrested