Janet, 42, arrived in London Tuesday night to support her big sister La Toya, 52, who's currently ensconced in the Big Brother house.

But it looks like Janet's the one who could really use the support.

The Damita Jo singer headed straight for Mayfair nightclub Mahiki where, despite hanging out until 2 a.m., she didn't have a drop of alcohol, according to the Daily Mail.

Then how to explain Jackson's hunched-over, sickly demeanor as she exited the club?

Did Jackson, who had to cancel her Rockwitchu tour in October after being hospitalized with an undisclosed illness, have a relapse?

Are those pregnancy rumors true after all, and was Jackson experiencing a bout of early-morning sickness?

While in town, Janet is expected to attend Thriller Live, the musical based on her brother Michael Jackson's music at the Lyric Theatre in London's West End.

Hopefully she rebounds before then and isn't confused with one of the zombie extras.