An outstanding question in astrophysics is the merger rate of supermassive black holes (SMBHs). An SMBH is thought to lie at the center of every large galaxy, so galaxy mergers are expected to be the precursor to SMBH mergers. Understanding if and how these eventual SMBH mergers happen requires also studying the stages of “dual” SMBHs and how they grow before becoming gravitationally bound to each other. We have recently completed a study of the hard X-ray emission from a merger system, Mrk 266, which we had previously claimed has two actively accreting SMBHs. In this paper (Iwasawa+) we model the X-ray emission and conclude that one of the accreting SMBHs lies behind a significant obscuring screen of dust and gas. This obscuring screen complicates the identification of such growing black holes using data from other wavelengths. Given the frequent “pile-ups” of gas and dust in galaxy mergers, it is possible that growing SMBHs have been missed in previous surveys which did not use the hard X-rays. The paper has been accepted for publication in Astronomy & Astrophysics and a preprint is available.