Fox got just what it wanted from a special edition of “House” last night: A big boost for its Wednesday schedule that dulled ABC’s usually sharp night at the same time.

“House,” in the second episode of a two-parter that kicked off Tuesday night, averaged a 6.2 overnight rating among adults 18-49 last night. That was 77 percent better than the 3.5 “Bones” earned in the same 8 p.m. timeslot last week.

It also gave Fox a big boost for the night versus the previous week. The network took the night easily with a 7.5 rating, more than double second-place CBS and third-place ABC and up 27 percent over the previous week’s average.

That “House,” which has set two new series highs in the past month in its regular Tuesday 9 p.m. slot after “American Idol,” would do well is not surprising in itself. But in a May sweeps period where the winner will come down to a thin margin, and with Fox and ABC currently tied for No. 1 for the season to date, any edge is significant.

And Fox certainly got it. While Fox was surging ahead, ABC was falling behind. Facing “House” at 8 p.m., the network’s “Alias” dipped to a potentially series-low 1.8 rating, 18 percent off the previous week’s 2.2 and just two weeks after the show delivered its best ratings of the season.

ABC’s nightly average was a 3.6, lifted because of a 6.2 rating for “Lost” at 9 p.m.

Meanwhile, Fox led among 18-49s, with a 7.5 rating and 20 share. CBS was second with a 3.7/10, ABC third with a 3.6/10 and NBC fourth with a 3.4/6. Univision was fifth at 1.6/4, UPN sixth at 1.5/4 and WB seventh at 1.0/3.

Fox took the early lead at 8 p.m. with a 6.2 for “House.” NBC was second with a 3.8 for “Deal or No Deal,” CBS third with a 2.9 for “Amazing Race,” UPN fourth with a 2.0 for “America’s Next Top Model,” ABC fifth with a 1.8 for “Alias,” Univision sixth with a 1.6 for “La Bella Mas Fea,” and WB seventh with a 1.4 for the season, and possibly series, finale of “One Tree Hill,” which did rise slightly week to week among the audience’s target 18-34s with a 1.9.

Fox held on to its lead at 9 p.m. with an 8.7 for the “American Idol” results show (11.4) and “Unan1mous” (6.0). ABC followed with a 6.2 for “Lost,” CBS with a 3.5 for “Criminal Minds,” NBC with a 2.9 for “Dateline,” Univision with a 1.8 for “Barrera de Amor,” UPN with a 1.0 for “Everybody Hates Chris” repeats, and WB with a 0.6 for “Bedford Diaries.”

CBS took over the lead at 10 p.m. with a 4.8 for “CSI: NY.” NBC was second with a 3.4 for “Law & Order,” ABC third with a 3.0 for “Invasion” and Univision fourth with a 1.5 for “Don Francisco Presenta.”

Fox also led the night among households with an 11.3 rating and 18 share. CBS followed with a 7.5/12, NBC with a 7.0/11, ABC with a 5.9/9, UPN with a 2.3/4, Univision with a 2.0/3 and WB with a 1.6/3.