When the crowd responded to the show so positively, we realized we were 'onto something'. [=we had done/discovered something important, special, etc.]
Scientists believe they are 'onto' something big. [=scientists believe they are close to making an important discovery]
Don't try to shift the blame 'onto' me. [=don't try to blame me instead of the person who should be blamed]
(..) ...it'll be the farthest away from home I've ever been. Come on,Sam. Remember what Bilbo used to say: -''It's a dangerous business,Frodo.'' -''Going out your door. You step onto the road,and if you don't keep your feet... ... there's no knowing where you might be swept off to. '' Sam. Wood-elves. (..)2001 The Lord of the Rings: The Fellowship of the Ring