His real name is Mark A. Landis, and he is a lifelong painter and former gallery owner. But when he paid a visit to the Paul and Lulu Hilliard University Art Museum in Lafayette, La., last September, he seemed more like a character sprung from a Southern Gothic novel.

He arrived in a big red Cadillac and introduced himself as Father Arthur Scott. Mark Tullos Jr., the museum’s director, remembers that he was dressed “in black slacks, a black jacket, a black shirt with the clerical collar and he was wearing a Jesuit pin on his lapel.” Partly because he was a man of the cloth and partly because he was bearing a generous gift  a small painting by the American Impressionist Charles Courtney Curran, which he said he wanted to donate in memory of his mother, a Lafayette native  it was difficult not to take him at his word, Mr. Tullos said.

The painting, unframed and wrapped in cellophane, looked like the real thing, with a faded label on the verso from a long-defunct gallery in Manhattan. Father Scott offered to pay for a good frame and hinted that more paintings and perhaps some money might come the museum’s way from his family. But when the Hilliard’s director of development chatted with Father Scott about the church and his acquaintances in deeply Roman Catholic southern Louisiana, the man grew nervous. “He said, ‘Well, I travel a lot,’ ” Mr. Tullos recalled. “ ‘I go and solve problems for the church.’ ”

Mr. Landis  often under his own name, though more recently as Father Scott or as a collector named Steven Gardiner  has indeed done a lot of traveling over the past two decades, but not for the church. He has been one of the most prolific forgers American museums have encountered in years, writing, calling and presenting himself at their doors, where he tells well-concocted stories about his family’s collection and donates small, expertly faked works, sometimes in honor of nonexistent relatives.