The Catechism in Questions & Answers

540. Can we connect with the departed?

By remembering the departed and praying for them, we have a connection with them.
Attempting to contact the departed through necromancy or channelling is forbidden by God and is thus a sin: “There shall not be found among you anyone [...] who [is] a medium, or a spiritist, or one who calls up the dead. For all who do these things are an abomination to the Lord” (Deuteronomy 18: 10-12).