Clarification of objects using questions


When I want to ask whether or not something I have is what I think it is, I
can't figure out exactly what to say.

> これは梅じゃないの? (Rising intonation)
>
> Is this not a plum?
>
> これは梅じゃないね。(Falling intonation)
>
> This isn't a plum, right?

How could I say something like

> "This isn't a plum?!" (With a sense of surprise)
>
> "Isn't this a plum?"

[For a different example, here is the following from
よつばと.](https://i.stack.imgur.com/lg3Av.png)

[Which is translated officially to this.](https://i.stack.imgur.com/AKnIc.png)

In my mind, the translation is "Aren't I dead?" I guess I don't know if I'm
being semantic or not, sorry.

