Television critic Mike Hughes recommends three shows tonight:

"GREY'S ANATOMY," 8 P.M., ABC; THEN "ER," 9 P.M., NBC.

ABC has the big plot lines tonight; NBC has the big guest stars. It adds up to a busy two hours in TV hospitals.

"Grey's Anatomy" has Derek learning that he has lost more patients than he saved. He wants to quit; Meredith won't give up on him.

Meanwhile, tests start to show what's been wrong with Izzie. Also, Bailey and the Chief continue to disagree about her plan to specialize in pediatrics; Adele (guest star Loretta Devine) tries to intervene.

For "ER," this is a night of guest stars from the show's first year -- Noah Wyle, Eriq LaSalle and Julianna Margulies -- plus Susan Sarandon. The main plot involves an organ-transplant crisis: Neela and Sam have the organs, but the plane that was supposed to take them has left.

"WARRIORS" DEBUT, 10 P.M., HISTORY

Some 2,000 years ago, this documentary says, the Mayan empire had 10 million people, with a capital twice the size of Athens.

Why did it crumble? Terry Schappert, who hosts this show, says evidence points to changes in warfare.

Schappert is an ideal host. He's been an Airborne Ranger and Green Beret, but he also speaks several languages and has a degree in anthropology. Here, he practices with the Mayan weapons -- blow gun, stone axe, spear-thrower and more -- many using sharpened volcanic glass.

At first, he says, Mayan warfare was brutal but small-scale; individuals were taken for sacrifice. One change came in 378 AD, when a non-Mayan city-state launched a new era of territorial attacks. Another came three centuries later, with the Mayans' first effort at annihilating a population. By about 900 AD, cities were no longer safe; people scattered and the jungle swallowed up a once-great empire.