Cheapest priced copy (Murders at Karlov Manor Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Confirm Suspicions 
Instant · Rare · Shadows over Innistrad · #53
Counter target spell.
Investigate three times. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Murders at Karlov Manor Commander | 97 | Rare | $0.49 | — |
| Shadows over Innistrad Promos | 53s | Rare | — | $0.79 |
| Shadows over Innistrad | 53 | Rare | $0.49 | $0.79 |
4 rulings from Wizards of the Coast
- 8 April 2016If an effect refers to a Clue, it means any Clue artifact, not just a Clue artifact token. For example, you can sacrifice Wrench to pay for Alquist Proft, Master Sleuth's activated ability.
- 8 April 2016Clue is an artifact type. Even though it appears on some cards with other permanent types, it's never a creature type, a land type, or anything but an artifact type.
- 8 April 2016You can't sacrifice a Clue to pay multiple costs. For example, you can't sacrifice a Clue token to activate its own ability and also to activate Alquist Proft, Master Sleuth's ability.
- 8 April 2016You can't cast a spell without choosing legal targets. If all of those targets become illegal, the spell doesn't resolve and you won't investigate.