55 cards where the color identity ≤ BU and (the text includes “clue” or the text includes “investigate”)

Academy Manufactor (Outlaws of Thunder Junction Commander #251)
Blink (Doctor Who #116)
Case of the Filched Falcon (Murders at Karlov Manor #44)
Cold Case Cracker (Murders at Karlov Manor #46)
Confirm Suspicions (Murders at Karlov Manor Commander #97)
Curious Cadaver (Murders at Karlov Manor #194)
Curious Inquiry (Murders at Karlov Manor #51)
Daring Sleuth // Bearer of Overwhelming Truths (Shadows over Innistrad #54)
Daring Sleuth // Bearer of Overwhelming Truths (Shadows over Innistrad #54)
Deduce (Murders at Karlov Manor #52)
Dimir Cluestone (Dragon's Maze #138)
Drag the Canal (Murders at Karlov Manor #199)
Drownyard Explorers (Shadows over Innistrad #56)
Eliminate the Impossible (Murders at Karlov Manor #54)
Eloise, Nephalia Sleuth (Midnight Hunt Commander #3)
Erdwal Illuminator (Murders at Karlov Manor Commander #104)
Ethereal Investigator (Murders at Karlov Manor Commander #105)
Excogitator Sphinx (Alchemy: Murders at Karlov Manor #6)
Five Hundred Year Diary (Doctor Who #42)
Fleeting Memories (Shadows over Innistrad #62)
Floodhound (Modern Horizons 2 #42)
Follow the Bodies (Murders at Karlov Manor Commander #23)
Foreboding Steamboat (Murders at Karlov Manor Commander #28)
Forensic Gadgeteer (Murders at Karlov Manor #57)
Foul Play (Innistrad: Midnight Hunt #101)
Gone Missing (Shadows over Innistrad #67)
Guess Your Fate (Unfinity #215a)
Hard Evidence (Modern Horizons 2 #46)
Havengul Laboratory // Havengul Mystery (Universes Within #9)
Havengul Laboratory // Havengul Mystery (Universes Within #9)
Hold for Questioning (Jumpstart 2022 #11)
Homicide Investigator (Murders at Karlov Manor #86)
Hostile Investigator (The Big Score #10)
Hotshot Investigators (Murders at Karlov Manor #60)
Inquisitor Eisenhorn (Warhammer 40,000 Commander #127)
In Too Deep (New Capenna Commander #27)
Jace's Scrutiny (Shadows over Innistrad #70)
James, Wandering Dad // Follow Him (Fallout #31)
Lazav, Wearer of Faces (Murders at Karlov Manor #216)
Magnifying Glass (Murders at Karlov Manor #255)
Martha Jones (Doctor Who #48)
Mistway Spy (Murders at Karlov Manor #65)
Nick Valentine, Private Eye (Fallout #35)
Osgood, Operation Double (Doctor Who #191)
Out Cold (Murders at Karlov Manor #66)
Persuasive Interrogators (Murders at Karlov Manor #98)
Piper Wright, Publick Reporter (Fallout #36)
Press for Answers (Shadows over Innistrad #80)
Secret Passage (Ravnica: Clue Edition #20)
Secrets of the Key (Innistrad: Midnight Hunt #73)
Senator Peacock (Ravnica: Clue Edition #2)
Tamiyo's Journal (Shadows over Innistrad #265)
Tangletrove Kelp (Murders at Karlov Manor Commander #24)
Toxin Analysis (Murders at Karlov Manor #107)
Trail of Evidence (Shadows over Innistrad #93)
Transmutation Font (The Big Score #28)
Unshakable Tail (Murders at Karlov Manor Commander #29)

This search is finished. Now the real work can begin.