''Walk the Line'': Joaquin and Reese on their risky duet

On a sweltering summer day in Mississippi, the cast and crew of Walk the Line are on location inside one of the Tunica area’s large-scale barge casinos, tricked out to resemble the Mint in Las Vegas in the 1960s. It’s a performance scene in which Joaquin Phoenix plays Johnny Cash not as the genial father figure and stoic balladeer he became in later years, but as a pill-popping, flop-sweating, emaciated, unhinged rock & roll wreck.

Phoenix runs limping onto the stage, launching into ”I Got Stripes” like a man with a train full of amphetamines to catch. Reese Witherspoon, as June Carter, looks alarmed, and she isn’t necessarily pretending: In take after take, Phoenix has insisted on bumping his leg on an amplifier as he trots on stage, to appear all the more believably stoned. He’s injured his leg badly enough that earlier I glimpsed him backstage pressing an ice pack to his knee. On top of that, each take has him falling unconscious midverse, and Phoenix isn’t the kind of actor to pass out gingerly.