At no time do the plain look so perfect as in early autumn.这里的倒装句为什么有个do?

正常语序应该是
The plain doesn't look so perfect as in early autumn at any time.
这里有doesn't这个助动词,那么当at any time变成at no time的否定形式放到句子开头倒装后,doesn't就便成肯定的does了
不知道说清楚没有～