  We propose a prescription for describing correlation functions in
higher-dimensional defect conformal field theories (DCFTs) by those in
ancillary conformal field theories (CFTs) without defects, which is a vast
generalization of the image method in two-dimensional boundary CFTs. A
correlation function of $n$ operators inserted away from a defect in a DCFT is
represented by a correlation function of $2n$ operators in the ancillary CFT,
each pair of which is placed symmetrically with respect to the defect. For
scalar operators, we establish the correspondence by matching the constraints
on correlation functions imposed by conformal symmetry on both sides. Our
method has potential to shed light on new aspects of DCFTs from the viewpoint
of conventional CFTs.
