Belden Place, the quaint and charming alley adjacent to the Financial District, is getting a new restaurant tenant this fall, and it's a full-service Mexican restaurant called Tin Cactus.

The owners are the same as Toy Soldier, the brewery/restaurant that opened on Belden two years ago. As they tell the Chronicle, they've snapped up the next-door space that used to be home to Sauce, with plans to open a "mid-tier" Mexican spot focused on Baja cuisine by October.

Co-owner Franz Meis, who along with executive chef Fred Turner used to work at Belden Taverna (in the space where Toy Soldier is now), says he's been keeping a Mexican-food journal since he was a kid, and this journal will help inform the menu at Tin Cactus. Dishes you're likely to see include Dungeness crab tostadas with jicama; chicken mole; and aguachile made with hamachi, avocado and plantain chips.

"The alley needs a kick in the pants,” Meis says to the Chronicle, regarding the former French-restaurant hub that's lost some of its sheen. "We bought the Sauce location because we want to have control of what happens next."

Also, there will be specialty cocktails, 60 tequilas, 20 mezcals, beers from next door, and new Mexican lagers that Toy Soldier brewer Aram Gutowski is working on.

The interior is being done by designer Michael Brennan, who also designed Zero Zero and Toy Soldier.

Customers at Toy Soldier will be able to get a preview of the food at Tin Cactus at the brewery's two-year anniversary party next week, on September 6.

Tin Cactus, 56 Belden Place, opening in October.