Mr. Gagosian. (Patrick McMullan)

The plot thickened today in the ongoing legal drama involving Larry Gagosian, Jan Cowles (the mother of retired Artforum editor and art dealer Charles Cowles) and a $2.5 million Mark Tansey painting, with The New York Post reporting that Ms. Cowles has slapped Gogo with a $14 million suit alleging that he sold the Tansey and another work, a $4.5 million Lichtenstein, without her consent.

Here's The Post:

"Court papers filed by Cowles last night state the Tansey, along with a $4.5 million work from Roy Lichtenstein’s “Girl in Mirror” series, were sold by her son, Charles, to Gagosian, 'without her knowledge or consent' in 2008-2009. Court papers say the Lichtenstein, in good condition, was shipped to art fairs, then sold to a mystery buyer for $2 million in 'damaged condition.'"

Ms. Cowles claims that the work was not damaged, and her lawyer hammered the world's most powerful dealer today, calling his behavior "blatant and egregious."

The Gagosian gallery fired back later in the day, telling The New York Times that the charges are "outrageous and baseless." The gallery is blaming Ms. Cowles's son, saying that he failed to mention that, no, the paintings were not his to sell. Mr. Cowles told The Times last year that he forgot that 31 percent of the Tansey was owned by the Metropolitan Museum of Art.

Last year, Mr. Gagosian agreed to pay British collector Robert Wylde $4.4 million for selling him the Tansey.

We'll be following this as it develops.