Homicide Investigator is a rare Creature — Human Detective card from Murders at Karlov Manor Promos (PMKM), collector number 86p. Current market price: $0.19 (foil $0.22), TCGplayer market prices via Scryfall.
Whenever one or more nontoken creatures you control die, investigate. This ability triggers only once each turn. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")