Adding a dictionary for each object inside another dictionary - ios

Question

I've populated a uitableview from an NSMutableDictionary using this code to populate my dictionary:
-(NSMutableDictionary *)createDictionaryForSectionIndex:(NSArray *)array withSubtitle:(NSArray *)subtitle
{
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
for (char firstChar = 'a'; firstChar <= 'z'; firstChar++)
{
NSString *firstCharacter = [NSString stringWithFormat:#"%c", firstChar];
NSArray *content = [array filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF beginswith[cd] %#", firstCharacter]];
NSMutableArray *mutableContent = [NSMutableArray arrayWithArray:content];
if ([mutableContent count] > 0)
{
NSString *key = [firstCharacter uppercaseString];
[dict setObject:mutableContent forKey:key];
NSLog(#"%#: %lu", key, (unsigned long)[mutableContent count]);
}
NSLog(#"mutable content: %#", mutableContent);
}
return dict;
}
from this source: https://stackoverflow.com/a/13279408/1042801
I'm trying to add another key/value for each outputted key/value. It's somewhat difficult to articulate my thoughts, so here's an example of something that I think I need:
key => 'A'
object => {"Aardvark"
object => {"mammal"}
, "Ape"
object => {"mammal"}
, "Aquaman"
object => {"superhero"}
}
//etc...
My table view should then be able to access those keys for each object above it to use as a detail text label for the cells in my table view. My apologies if what I'm trying to accomplish makes no sense, dictionaries aren't quite engrained in my repertoire yet.