Alfonso Soriano, who hit a game-winning single in the ninth Thursday to beat the Chicago White Sox, drew a two-out walk in the 10th from Luis Vizcaino (1-3) and stole second. Theriot followed with a grounder that took a crazy bounce past first baseman Victor Martinez.
The Cubs trailed 7-0 against Cliff Lee going into the fifth and were still down 7-2 in the eighth.
The Indians loaded the bases off Kevin Gregg (2-1) in the 10th before Kosuke Fukudome made a nice catch of pinch-hitter Ryan Garko's liner to center field. The Cubs beat Vizcaino, whom they released earlier this season.
Wood, who saved 34 games for the Cubs last season and spent a decade with the team before signing with Cleveland as a free agent in the offseason, got a rousing ovation when announced in the bottom of the ninth in his return to Wrigley Field.
But after retiring Milton Bradley, he served up Lee's homer. The crowd of 40,155 went wild as Wood absorbed his third blown save in 11 chances.
The Indians took their big lead behind Lee, last year's AL Cy Young winner, on three-run homers from Luis Valbuena and Martinez.
Homers by Reed Johnson in the fifth and Derrek Lee in the sixth cut it to 7-2.
Joe Smith relieved for the Indians after Bradley opened the eighth with a single. Geovany Soto doubled, Johnson walked and a bases-loaded, two-run single by Andres Blanco made it 7-4.
Facing reliever Rafael Perez, pinch-hitter Koyie Hill hit a hard grounder that went off third baseman Jhonny Peralta for an error, cutting it to 7-5. Soriano then delivered an RBI single that made it a one-run game.
Former Cubs player Mark DeRosa also made his return to Wrigley. He got a standing ovation in his first at-bat and went 1 for 3 with two walks and an RBI.