In English, the words used when making the Sign of the Cross are:
In the name of the Father, and of the Son, and of the Holy Spirit. Amen.
The German translation is:
Im Namen des Vaters und des Sohnes […]
While I understand that the possessive der Vater takes the genitive case as des Vaters. I don’t understand why der Name, which is possessed by der Vater, takes what appears to be the dative case definitive article dem and an additional n. Is Namen plural, and if so, shouldn’t the article therefore be den?