Can someone explain the difference between rape and aggravated rape to me?

According to the Tennessee criminal code, both aggravated rape & especially aggravated kidnapping are Class A felonies with 15-year-SoL’s. But I am wondering about this proviso in the section on criminal procedure:

*No period during which the party charged conceals the fact of the crime, or during which the party charged was not usually and publicly resident within the state, is included in the period of limitation.

[Code 1858, § 4988; Shan., § 6947; mod. Code 1932, § 11488; T.C.A. (orig. ed.), § 40-205]*

I don’t know what would be required for concealing the fact of the crime. As I envision the scenario, the protagonist’s husband, around the age of 18 or 19 abducted and raped the victim; it’s about 16 years later, and he’s never left the state in the interim. He was never a suspect; in fact I don’t think the victim ever made a complaint. Would the mere fact of not coming forward and confessing count as “concealing the fact of the crime”?

Isn’t kidnapping a federal crime? (or do they have to cross state lines? Or does it have to be for ransom?) I would be surprised if the statute of limitations for that is anything escapable.

Am I reading this right – it takes TWO people to commit aggravated rape on a mentally incapacitated person (assuming a weapon or coercion are not involved)?

No. Hiding the body would probably do it in a murder case. In a rape/kidnapping scenario, I dunno…maybe drugging the victim so she doesn’t remember the crime and cleaning up any DNA evidence would qualify. Still, I find it bordering on implausibility that such a horrific event taking place over several days would go unreported. Somebody would likely have reported the girl missing, and when she resurfaced, there would be questions…

I’m still thinking the story through rather than writing it. Other than the few things I mentioned in the OP, I’m not committed to anything yet.

ETA: Also, the victim obviously remembers the husband; that’s the engine for the plot happening.

Also, now that I think on it, my best friend from high school was held captive in her home and raped over the course of two days, and her parents pressured her not to report it as they didn’t want the “shame” falling upon them. Happily she already knew that they were…touched…and ignored them, but I can imagine such a crime happening to a younger and less mature woman and her succumbing to such insanity.