Unlike many game shows that seem to get dumber as the prize amounts grow ever higher, the new series “Merv Griffin’s Crosswords” (syndicated, check local listings) demands that players think quickly on their feet.

When it begins, “Crosswords” seems closer to Scrabble, with players filling in the letter blanks for individual words. Most words garner a reward of between $100 and $300. But as they progress, the words form connections and the puzzle takes shape. After a winner is declared, he or she gets to complete the full puzzle in a lightning round for a bonus prize of $2,000.

Like “Jeopardy,” another Griffin production, “Crosswords” will appeal to game-show buffs eager to give their gray matter a workout.

¢ The probing documentary “Falling Man” (8 p.m., Discovery Times) recalls one of the most powerful photographs to emerge from the terrorist attacks of 9/11 – a victim descending to his death from the North Tower of the World Trade Center. After news outlets ran the picture in their Sept. 12 editions, they were besieged with complaints from outraged readers. The photo all but vanished from history.

But many photographers and editors still consider it to be a powerful depiction of the horror of the day. “Falling Man” includes interviews with family members of victims of the attacks and with journalists who tried to find out just what happened to the picture and to the man who may be its subject.

Tonight’s highlights

• On back-to-back episodes of “Prison Break” (Fox), time to stop T-bag (7 p.m.) and take on Mahone (8 p.m.).
• Hiro’s sword heist goes awry on “Heroes” (8 p.m., NBC).
• Larry King, Rep. Loretta Sanchez, Dominick Dunne and Rikki Klieman guest-star on “The Closer” (8 p.m., TNT).