Darren Stokes is playing the god Neptune in Chicago Opera Theater's production of Monteverdi's Il ritorno d'Ulisse in patria, which opened this week at the Harris Theater and has its second performance tonight. The 33-year-old bass-baritone is a first-year member of the Ryan Opera Center, the young artists program at Lyric Opera of Chicago — which means that he has to perform in Lyric's annual "Rising Stars in Concert" program, which is also tonight and across town at the Civic Opera House.

For Stokes to pull out of the Monteverdi for the one evening would be a dirty trick: the role is hardly standard repertoire, so there aren't a lot of basses around who know the part and could fill in on short notice. What to do?

As it happens, Neptune appears only in Acts I and V of Ulisse. There's plenty of time in-between, so Lyric agreed that Stokes could do his early scenes, leave the Harris Theater, dash over to the Civic Opera House to sing his "Rising Stars" numbers, and dash back to finish the Monteverdi. COT went along with the plan — with one condition: that he not take off his Neptune stage makeup, which takes quite a long time to apply.

So Stokes will be singing to his colleagues and to Lyric Opera patrons colored like a blue-green creature from the briny deep. Maybe it's fitting that he'll be performing one of Mephistopheles's arias from Gounod's Faust.

Lyric Opera of Chicago's "Rising Stars in Concert" program, featuring members of the company's Ryan Opera Center in various arias, duets and ensembles accompanied by members of the Lyric Opera Orchestra under conductor Philip Morehead, is tonight at 7:30 p.m. in the Ardis Krainik Theatre at the Civic Opera House in Chicago's Loop; tickets by invitation only. Chicago Opera Theater's Il ritorno d'Ulisse in patria, conducted by Jane Glover and directed by Diane Paulus, is tonight and April 5 and 7 at 7:30 p.m. and April 1 at 2 p.m. at the Harris Theatre for Music and Dance; information is available at www.chicagooperatheater.org.