Ka-pow!

Comic book legend Frank Miller — who penned “The Dark Knight Returns” and “Sin City” — socked his ex-wife with a lawsuit Monday for allegedly swiping valuable rough sketches of his work and trying to sell them under the table.

Lynn Varley, an award-winning comic book colorist who collaborated with Miller on many of his early tomes, is allegedly hiding preliminary sketches she squirreled away before the couple’s divorce, Miller claims in his Manhattan Supreme Court lawsuit.

Varley filed for divorce in 2006, after 20 years of marriage. In 2011, while the duo was still married, they cut a deal to divvy up illustrations and artwork they owned, according to the court documents.

The agreement didn’t give Varley ownership of the rough sketches, which she allegedly grabbed either from the couple’s co-op or from a storage unit during their marriage.

“Varley continued to conceal the fact that she had taken the Roughs throughout the couple’s divorce proceedings and even after they had negotiated and entered into a postnuptial and predivorce agreement which provided that Varley was only entitled to receive specifically designated pieces of Miller’s artwork, not including the Roughs,” the suit states.

While not generally as valuable as published comic book illustrations, the roughs “are nevertheless sought after by collectors of comic art, particularly where the artist is of Miller’s influence, renown and stature in the comic book industry,” according to the court docs.

Varley has been trying to surreptitiously hawk the sketches through a dealer at various comic conventions, including San Diego Comic Con and the Lake Como Comic Art Festival, the lawsuit alleges.

“Despite Varley’s efforts to sell the Roughs through her art dealer in secret, Miller has discovered that Varley’s art dealer was offering the Roughs for sale ‘under the table’ to collectors,” the suit states.

Miller believes some of the sketches may have already been sold off.

He’s asking for the sketches back immediately and for an injunction to stop Varley from selling or destroying them — in addition to damages of at least $25,000 to be decided in a jury trial.

Miller used the sketches as reference during final composition of various comics and illustrations, according to the suit, which does not outline which works the sketches are from.

Varley couldn’t immediately be reached for comment.