This is a last great gasp of mainstream Sundance Film Festival cinema in which a feisty independent-living grandma treks across L.A. to get even with a telephone fraudster who almost got the best of her. Josh Margolin’s Thelma (B) features a mighty performance by the wonderful June Squibb and another by the late, great Richard Roundtree as a friend from a neighboring nursing home with one last great adventure left in him as well. Fred Hechinger is a hoot as her technology enabling grandson, but Parker Posey and Clark Gregg don’t have much to do as his parents. The film is at its clever best as it follows a sleuthing spy type storyline, with hearing aid volume controls and GPS identity bracelets subbing in for the kinds of gadgets Q used to whip up in the lab. As Thelma, Squibb is a fully rounded character with spunk, sass and a sharp mind. The film fully humanizes her character, even though the script and story could have been much stronger. Still, it’s a fun lark and a great chance to watch Squibb and Roundtree whoop it up.