Vengeful Tracker

Whenever an opponent sacrifices an artifact, Vengeful Tracker deals 2 damage to them.

Frantic Scapegoat

Haste
When Frantic Scapegoat enters, suspect it. (It has menace and can't block.)
Whenever one or more other creatures you control enter, if Frantic Scapegoat is suspected, you may suspect one of the other creatures. If you do, Frantic Scapegoat is no longer suspected.

Lightning Helix

Lightning Helix deals 3 damage to any target and you gain 3 life.

Person of Interest

When Person of Interest enters, suspect it. Create a 2/2 white and blue Detective creature token. (A suspected creature has menace and can't block.)

Bother

Create three 1/1 colorless Thopter artifact creature tokens with flying. Surveil 2.

Fuss

Put a +1/+1 counter on each attacking creature you control.

Fuss // Bother

Auspicious Arrival

Target creature gets +2/+2 until end of turn. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Case of the Gateway Express

When this Case enters, choose target creature you don't control. Each creature you control deals 1 damage to that creature.
To solve — Three or more creatures attacked this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Creatures you control get +1/+0.

Meddling Youths

Haste
Whenever you attack with three or more creatures, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Gadget Technician

When Gadget Technician enters or is turned face up, create a 1/1 colorless Thopter artifact creature token with flying.
Disguise {U/R}{U/R} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)

Dog Walker

Vigilance
Disguise {R/W}{R/W} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)
When Dog Walker is turned face up, create two tapped 1/1 white Dog creature tokens.

Neighborhood Guardian

Whenever another creature you control with power 2 or less enters, target creature you control gets +1/+1 until end of turn.

Karlov Watchdog

Vigilance
Permanents your opponents control can't be turned face up during your turn.
Whenever you attack with three or more creatures, creatures you control get +1/+1 until end of turn.

Inside Source

When Inside Source enters, create a 2/2 white and blue Detective creature token.
{3}, {T}: Target Detective you control gets +2/+0 and gains vigilance until end of turn. Activate only as a sorcery.

Case of the Burning Masks

When this Case enters, it deals 3 damage to target creature an opponent controls.
To solve — Three or more sources you controlled dealt damage this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Sacrifice this Case: Exile the top three cards of your library. Choose one of them. You may play that card this turn.

On the Job

Creatures you control get +2/+1 until end of turn. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Reckless Detective

Whenever Reckless Detective attacks, you may sacrifice an artifact or discard a card. If you do, draw a card and Reckless Detective gets +2/+0 until end of turn.

Shock

Concealed Weapon

Equipped creature gets +3/+0.
Disguise {2}{R} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)
When Concealed Weapon is turned face up, attach it to target creature you control.
Equip {1}{R}

Bolrac-Clan Basher

Double strike, trample
Disguise {3}{R}{R} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)

Museum Nightwatch

When Museum Nightwatch dies, create a 2/2 white and blue Detective creature token.
Disguise {1}{W} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)

Torch the Witness

Torch the Witness deals twice X damage to target creature. If excess damage was dealt to that creature this way, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Red Herring

Haste
Red Herring attacks each combat if able.
{2}, Sacrifice Red Herring: Draw a card.

Novice Inspector

When Novice Inspector enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Galvanize

Galvanize deals 3 damage to target creature. If you've drawn two or more cards this turn, Galvanize deals 5 damage to that creature instead.

Marketwatch Phantom

Whenever another creature you control with power 2 or less enters, Marketwatch Phantom gains flying until end of turn.

Perimeter Enforcer

Flying, lifelink
Whenever another Detective you control enters and whenever a Detective you control is turned face up, Perimeter Enforcer gets +1/+1 until end of turn.

Seasoned Consultant

Whenever you attack with three or more creatures, Seasoned Consultant gets +2/+0 until end of turn.

The Chase Is On

Target creature gets +3/+0 and gains first strike until end of turn. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Makeshift Binding

When Makeshift Binding enters, exile target creature an opponent controls until Makeshift Binding leaves the battlefield. You gain 2 life.