The Compton Mirror in NGC 4151
  We show that the sharp cutoff in the hard X-ray spectrum of NGC 4151, unusual for Seyfert 1 galaxies, can be reconciled with the average Seyfert 1 spectrum if we assume that the central source is completely hidden from our line of sight by the thick part of the accretion disk or by the broad emission line clouds. The observed X-ray radiation is produced by scattering of the Seyfert 1-type spectrum in the higher, cooler parts of the accretion disk corona, or in a wind. A sharp cutoff appears as a result of the Compton recoil effect. This model naturally explains a discrepancy regarding the inclination of the central source, inferred to be low (face-on) from observations of the iron $K\alpha$ emission line, but inferred to be high on the basis of optical and UV observations. 
Juri Poutanen, Marek Sikora, Mitchell C. Begelman, and Pawel Magdziarz