Sammendrag
In this article we classify all the smooth 3-folds of P5 with an apparent 4-tuple point provided that the family of its 4-secant lines is an irreducible (first order) congruence. This is sufficient to conclude the classification of all the smooth codimension two varieties of Pn with one apparent (n-1)-point and with irreducible family of (n-1)-secant lines.