David Cook’s set leaves little doubt whether he is truly a rock star. The singer who created so many show-stopping, take-your-breath-away moments in the Idoldome showed he could do the same before a group of 12,700. His set contained one amazing piece of news as well, as he announced he had just learned that morning that his brother’s tumor had “stopped growing.”

He then broke into an extra joyous run through “My Hero,” dedicated to his brother. Throughout the season, Cook no doubt wary that it would seem a manipulative plea for sympathy, avoided making direct reference to his brother’s illness, attributing the bracelet he wore in support of cancer victims to a suffering little girl. Now, finally that he has been given some good news, he at last shared it with the audience. One can’t help feeling that he is a very rare class act, Mr. David Cook.

The screams were split pretty evenly between David A. and David C., who immediately followed. Cook can come off as cocky on stage; constantly exerting the crowd to get up by waving his arms seemed a bit bold for someone who couldn’t have filled a bar in Glendale last year, much less an arena. But then Cook discussed a sibling who is suffering from cancer: “My brother’s tumor has stopped growing!” he happily told the crowd, and it was hard not to be touched. His set was uneven, though his spooky Michael Jackson-by-way-of-Chris Cornell version of “Billie Jean” sure was hard to beat.

For the encore, all 10 vocalists were on stage, marching back and forth across the stage while singing Rihanna's "Don't Stop the Music." Brooke and Jason both seemed a bit sheepish; David C. grinned happily and David A. looked up at him like a proud little brother. Hey, if you have to throw a group number in there for a closer, this wasn't a bad way to end a fun night.

“I bought this camera for the sole purpose of documenting what I'm expecting to be the coolest summer of my life,” Cook announces, before having the house lights turned up and turning his lens on the audience and giving a shout-out to newly married Ruben Studdard. Then what bedeviled Brooke befalls Cookie: “I lost an ear (monitor) but I’ll keep it out.”

He grows grateful -- “We are just 10 people who got crazy lucky” –- and sings about how he’s having the Time of My Life –- for more poignant reasons than music superstardom, it turns out. “I got great news today,” he says. “My brother’s tumor has stopped growing!” Wild cheers. “Thank you, guys, from the bottom of my heart.” He dedicates the Foo Fighters' My Hero to his brother. “How loud can you guys get?” Very loud, it turns out.

After he jogs around the stage, a very dark and very pregnant pause ensues. Then, like Michael Jackson at the Grammys oh-so-many years ago, there’s a theatrical entrance: Cookie solo at the stage’s edge, standing in front of a literal smokescreen (psychedelic smoke images are billowing on the wall behind him) -- just him, his guitar, a mike and Billie Jean.

Finally, the group finale, Rihanna's Don’t Stop the Music, for which the Idols have tweaked or overhauled their outfits. Carly’s in sparkly tight satin, Syesha’s in Rhianna-ready booty shorts and Brooke is in some Stevie Nicks-esque, cape-like floral robe. Michael’s draped in one of his scarves (purple velvet), while Jason seems to be winking -– or is that smirking? -- through the whole act.

After the Idols leave, after the lights go up, Cookie briefly returns to the stage and hands a T-shirt to a fan. Girls cram the edge of a metal balcony above. A piece of paper flutters down to where their No. 1 Idol is striding through. He catches it, borrows a pen and signs it as the chorus of “We love yous!” grows. -- O.B.