Akagawa Jirō is a real household name in Japan, when it comes to mystery novels (plus, a gazillion dramas and/or movies adapted from them!), and particularly loved are his series about Holmes, The Calico Cat, and about these Three Sleuthing Sisters (I have no idea why, for this adaptation, they felt the need to add an extra sister, LOL...but since they're all cute, nice and funny, I'm not gonna complain...^_^;...)
It's therefore no surprise that the mystery plots featured in this drama were well written and always interesting; mystery fans won't be let down.
Acting-wise, though, don't expect too much: the guest stars were, in all honestly, mostly terrible and contributed greatly in bringing down the average acting grade; the main cast did ok though (I must confess not being a fan of Namase Katsuhisa normally, but he was particularly good here, and the comic relief scenes between him and the always funny Muroi Shigeru were mostly hilarious; too bad Takenaka Naoto's part is so small, as he was just a ghostly presence throughout the whole series, except for one episode where he actually appeared in flesh and had some screentime). Oh, talking about episodes, as it's always to be expected in this type of drama, some were better than others.
Last but not least, the music commentary was always on spot, imho, and added to the overall quality.
All in all, a nice mystery interspersed with comedic elements and a nice family in the center of it all.
It felt much older than it actually is (in the best sense possible: I mean it reminded me of a drama from the Golden Era! ^___^)