* "D" refers to "disappearing act" and "Doctor" (Isaka gets focus this week)
* #27 is titled "The Invisible Magical Lady"; #28 is "Do or Die Twin Maximum"

Our story begins with our heroes (Shotaro, Phillip and Akiko) at a dinner in one of those fancy restaurants... except Shotaro isn't happy with Terui Ryu being invited along for whatever reason, while Phillip is more interested in working on the second item Shroud has sent to them. Turns out there's evening entertainment in this restaurant as well - a magic act to be precise, by the highly experienced Frank Shirogane, who's taken the opportunity to debut his granddaughter Lily Shirogane. Except she turns out to be a bit of a [[CuteClumsyGirl klutz]], who somehow pulls off the disappearing act easily enough.

The action (for want of a better term) moves back to Narumi Detective Agency, where Phillip puts the finishing touches on the newest Memory Gadget - the Denden Sensor, a snail with a special Gaia Memory that can detect anything with infrared. For some reason it goes off, and Shotaro starts looking around - only for ''something'' to knock him over and halfway across the office. And then that something ''materialises'' on top of him. It's ''Lily Shirogane'' herself, conveniently explaining the secret to the whole disappearing act.

After Shotaro takes a little too long to get out from under her, we learn that this secret involves one of those ''Dopant Memory tattoos'' on her arm. And that's not all... the Invisible Memory has been acting out of whack, not only triggering itself on and off at random, but until now has ''refused to emerge on deactivation''. True enough, it trips on again while she's explaining all this - but the Denden Sensor has infrared goggles for an altmode, allowing Phillip to see her in this form, revealing that the Invisible Memory doesn't turn her into some grisly Dopant form, just invisible. The mystery deepens as our heroes learn that the Invisible Memory didn't come from one of those Dopant Memory sellers like Kirihiko used to do, god rest his soul, but handed to her when she needed it the most - by some guy in a tuxedo and carrying an umbrella.

Meanwhile at the Sonozaki mansion, Ryuubei notices Wakana going through some mood swings, getting particularly annoyed with Saeko going off to meet with hat Dr Isaka yet again - but it's the fact that she somehow ''breaks her teacup with one hand'', apparently involuntarily, which draws his concern. Wakana brings up Isaka's examining her Dopant Driver as well, which is when Ryuubei decides to find Isaka and talk to him about this.

Our heroes' investigations go into full swing, as they manage to track down this new Dopant guy at ''the piano bar'' he's most often seen at, just as Terui Ryu notices Shotaro and Akiko going around town, and opts to tail them. Only Lily is actually with them the whole time, and she decides to head straight to the piano bar without them - whereupon she bumps into Ryu and knocks him over before reappearing, just like before. Except that Ryu doesn't take kindly to it at all, and the two are at loggerheads almost immediately.

Sure enough, we finally get to the piano bar, and things go swimmingly as they find the man they're after behind said piano. A little too swimmingly, as the man, without even getting his ''bowler and umbrella'', recognises Ryu by name and reveals that he paid his family a visit one time... ''with the Weather Memory in hand.'' It's too late to do much of anything as ''Dr Isaka'' immediately jacks in and turns into the Weather Dopant before them, raising a mini-thunderstorm to mask his escape. It's Rider time for Shotaro, who goes into Double first and tries to take down Weather Dopant - who turns out to be a lot tougher than he expected, shrugging off a FinishingMove with a massive cold front. As Shotaro and Phillip debate using their next available Memory for a doubly-powered Memory Break, Ryu as Accel moves in to assist (read: take revenge), but it doesn't quite pan out either, as Lily actually takes Dr Isaka's side, asking him to fix up the Invisible Memory. As in, fixing it so it'll work for her magic acts, rather than take it out and be done with it. Ryu can only shove the Engine Blade into the concrete in frustration as the Weather Dopant makes good his escape.

We return to Narumi Detective Agency, where Phillip's research has just been competed - simply linking the deaths from freezing (read: Ryu's family) to the Ice Age Dopant case had prevented them from seeing the big picture, as the Weather Dopant memory is quite literally a SuperpowerLottery, and likely responsible for some unexplained deaths from electrocution and drowning that took place well before the Ice Age case but ''around the same period that Ryu lost his family''. Which is all Ryu cares about now, ready to take down Dr Isaka and Lily just for being near him.

It's up to Shotaro to save Ryu from himself now, as he does his own research at the police station and gets ready to track down Isaka for himself. Unfortunately, not only do Jinno and Makura remain blissfully oblivious, but they're more concerned over the data they dug up on Lily Shirogane - having lost both her parents early on, she wound up raised by her grandfather and trained in her father's stead in magic all this time. It's also about this time when Shotaro and Akiko ''finally'' remember Dr Isaka from the Liar Dopant case, or more precisely, from looking for a doctor for Yukiho and finally getting her to Dr Isaka during the Liar Dopant case (whew).

Speaking of Dr Isaka, he's looking over Lily at the moment (well, as far as "looking" applies to an invisible person anyhow), and making Saeko somewhat jealous at this point. She goes off to the corner in a huff, just as Lily's condition is conveniently stabilised... which is precisely when Ryu bursts in on them, ready to bring an end to it. Fortunately Lily gets one chance to flee the scene, as Isaka explains that getting Ryu's father wasn't a completely random choice since the senior Terui, a veteran cop before Ryu, had been looking into Dopant cases on his own. Ryu isn't in a listening mood, going straight into Accel, which is just as well since Isaka is ready to go into Weather and take him on.

Fortunately, Shotaro isn't far away, and ready to go into Double to intervene, but things get sticky as Accel directs his anger at Double as well, just for interfering. Which makes it far too easy for Weather to take them both on, busting out one weather-based attack after another and keeping Double on his toes with the form-changing. Weather takes the time to explain how the Weather Memory's unique ability to channel several weather-based memories at one go is the only thing close to satisfying his lust for power - but he's out for more, using test subjects like Lily to cultivate more Dopant Memories for his own use, using a process that will eventually kill her. Apparently it's this procedure of using Gaia Memories without some kind of belt that gives him an edge over everyone else, which he demonstrates by shrugging off Accel's next attack, knocking him back and reverting him to Ryu, who finally realises that all the stuff Shroud handed to him and all that he's been through have officially amounted to ''nothing''.

At long last, all of Ryu's pent-up anguish this whole week reduces him to tears... which causes Shotaro as Double [=HeatTrigger=] to take things into his own hands, readying his Trigger Magnum for one [[FinishingMove Maximum Drive]] while shoving the remaining Heat Memory, against Phillip's protests, into the only slot available. Yes, it lets out a TREMENDOUS blast, but also has the unfortunate effect of ''burning out Shotaro's body'' and leaving him unconscious on the ground. Worst of all, Weather is not only intact but very much alive - but possibly not without help, as the scene starts dripping with NightmareFuel and ''Terror Dopant himself'' shows up to bail Isaka out. There's nothing more our heroes can do now, as Ryu scoffs Shotaro's attempts to help him out, while Shotaro vehemently believes Ryu will do the right thing eventually. And Saeko, having followed them from the clinic, saw the whole thing.

Back at Narumi Detective Agency, Phillip reveals his findings about Lily's unique Dopant Memory condition, and with Shotaro now laid up in bed, he's going to need Ryu's help on this one - but once again, Ryu is more concerned with finding Isaka, hitting Phillip before running off on his own. True enough, Isaka's had to abandon his clinic in the wake of these events and is now hiding out at the Sonozaki mansion, but Ryuubei's doubt over him is going to make it harder for Isaka to make him come around as well. At least until Isaka reveals the extent of his dedication to Dopant Memory development, in the form of ''several Dopant Memory connectors all over his chest''. Despite Wakana's protests, Ryuubei is finally convinced to let him stay around, even if Isaka does eat ten times as much as... well, ''anybody''.

In the meantime, Phillip elects against tracking down Ryu again, leaving Akiko to do it herself. By which we mean barging into the police station and ''whacking'' the required information out of Makura. With ''slippers''. Turns out Ryu's been carrying out a self-declared stakeout just outside Lily's home - which Akiko naturally assumes is because he really does care, but Ryu maintains that she's the only remaining lead to Isaka. Whichever it was, none of it matters as Frank Shirogane catches them in the act... and invites them in.

In between showing off a couple of tricks to Ryu and Akiko, treating them very much like the kids that make up his usual audience, Frank reveals that he's been expecting a backlash for some time, having known about Lily's Dopant Memory involvement from the beginning. As far as the magic acts are concerned, all's well and good if the illusions are pulled off without a hitch, but Frank is is ready to place Lily's wellbeing above that if need be. Sure enough, Lily appears at the door, causing Ryu to forget everything he's learned and go after her like a bloodhound - at least until he catches up to her, and instead of anything related to Isaka, he tells her instead to give up the Invisible Memory before it kills her. Unfortunately Lily confirms all of Frank's suspicions, insisting that she needs the Invisible Memory to pull off Frank's last big magic act before he retires, regardless of how she turns out... all of which basically takes Ryu's obsession over killing Isaka, and rubs it in his face. Ryu finally decides to let Lily do her thing one last time, making sure to be around once she's done. Meanwhile, Isaka decides he's settled in to Sonozaki mansion living, and makes his move...

It's time for that big final act Frank's been planning, and Ryu is in the back of the audience when Akiko and Phillip find him. Yes, they'll be able to get their act together and get the Invisible Memory out of Lily - but Ryu still owes Phillip one in the face from before. [[CallBack Just as Shotaro would have it.]] Problem is, Isaka managed to gatecrash on the event, and has no problem with getting Ryu out of the picture while observing how Lily and the Invisible Memory are coming along - but this time Ryu is ready for the people around him to help him, even bringing in the Accel Gunner to hold off Isaka as Weather Dopant while they make their escape.

The magic act goes off without a hitch... until Lily starts relapsing from the Invisible memory, but manages to make it backstage before anyone notices, meeting up with Ryu just as planned. Except it may be too late, as Lily actually DisappearsIntoLight before their eyes, but Phillip has the Denden Sensor on hand, using it to reveal Lily still standing there... whereupon Ryu as Accel delivers the killblow.

Except it's not, as the Invisible Memory finally reveals itself after her heart has stopped, but a jab from the Engine Blade set to Electric ''brings her back to life''. And Isaka as Weather doesn't even have time to curse himself for not thinking of it first, as Accel takes the Invisible Memory and cracks it with one hand. At last, our heroes have gotten Isaka's goat, and he goes postal on Accel with a few moves he hasn't used yet - until the Fang Memory joins in the action. Turns out Shotaro's also regained consciousness, and the fact that it's Phillip out in the field allows them to go into Double as [=FangJoker=] to take the battle to the enemy. Finally, our heroes get their act together and pull a combined FinishingMove that forces Weather to beat a retreat. And this time it's Shroud who's been hiding in a corner, watching the whole thing.

Things end on a high note for once - Ryu successfully gets Lily off the hook for Dopant memory involvement, but Isaka's first real defeat takes less priority than his ever-raging appetite. ([[EatTheDog Mick, don't just stand there, hide!]]) When Ryu pops over to Narumi Detective Agency for coffee, they suddenly get a surprise visitor. Lily Shirogane, who's specifically after Ryu, to thank him personally. Yes, like ''that''. Guess Ryu's got more than just Electric in his Engine Blade, eh?

[[CatchPhrase Just don't ask Ryu any questions.]]

!!Tropes include:
* CallBack: Phillip hitting Ryu just as Shotaro hit him back in the first episode.
* ChekhovsGun: The Twin Maximum. One Rider attempting it fails. Two Riders doing their own Maximum Drive at the same time is not only safer, but works out better.
* ContrivedCoincidence: Getting the Denden Sensor at the same time as an ''invisible client'' should count. Possibly justified by [[XanatosSpeedChess Shroud timing the release of her stuff in reaction to Museum's activity.]]
* EurekaMoment: Shotaro and Akiko only remember that Isaka was a doctor when they come across Santa-chan on his way home from the hospital.
* ExplosiveOverclocking: The effect of using two Gaia Memories at once for Maximum Drive.
* {{Foreshadowing}}: Isaka has a theory about how Gaia Memories rely on compatibility with their hosts to evolve. This is actually a plot point in ''[[TheMovie Forever A to Z]].''
** Shroud comments on the teamwork between Ryu and Phillip in her one appearance.
* HeelRealisation: Ryu.
* LoopholeAbuse: The Gaia Memory will only eject from Lily when she dies. Isaka never accounted for the possibility of restarting her heart.
* MundaneUtility: Relying on Dopant Memories for ''magic acts''.
** The Engine Blade works as a MagicalDefibrillator.
* NotSoDifferent: Ryu and Lily, eventually.
* ShipTease: Forgetting all the events of previous episodes, we now have [[RescueRomance Ryu and Lily]] - [[ShipperOnDeck and Akiko approves!]]
* ShoutOut: Isaka has exactly [[FistOfTheNorthStar seven Living Connectors on his chest]].
* VillainousBreakdown: This is the first time our heroes beat Weather Dopant. It won't be the last.