A hypnotist's show turns out to be way more than Zack bargains for when he is pulled out of the audience, put into a trance, and his body is "taken over" by the spirit of someone from the past. And that's only the beginning, because the stubborn spirit won't go away when the show's over! It's hard enough having just one self to worry about. What will Zack do with two?

這次札克和好友史賓賽一起參加「連老爺冰淇淋大賽」，優勝者不但可以得到一百元美金、一年免費的冰淇淋，還有還有，札克和史賓賽的照片還會被刊在《紐約時報》上呢！他們想了好多種口味的冰淇淋，像是花生醬水母、「睛」聲尖叫和巧克力黑猩猩，最後他們竟然以「喀滋喀滋腰果」入圍了最後五強呢！札克為了要告訴史賓賽這個好消息，馬上衝去他家告訴他。

不過史賓賽倒是很鎮定地做著實驗，一點都沒有興奮的樣子。札克覺得掃興極了！還大聲嚷嚷著口渴，把史賓賽桌上的檸檬汁給一口吞下！可……可是，札克喝下的竟然是史賓賽調製的「隱形藥水」！這下該怎麼辦呢？「連老爺冰淇淋大賽」就要來臨了，札克如果還是隱形的話，怎麼參加呢？