Well arturopkmn...it's a story about love, deception, greed, lust and…unbridled enthusiasm.

You can read about it here:
http://coerll.utexas.edu/gg/gr/cas_01.html

After that, the answer you're looking for lies here (Specifically under "Indefinite articles"):
http://en.wikipedia.org/wiki/German_declension

If you want the Coles' notes version, it is "einen" because it is in the accusative case.

Hope that helps, and enjoy the read.

"Ein" means "a/an" for masculine and neutral words that practice the action (subject). "Einen" means "a/an" for masculine words that recive the action (object). For example: "Ein Junge isst einen Apfel".

In German there are four major "cases": nominative, accusative, dative and genitive. ein (masculin a) is used in the nominative case. Nominative case is when the noun is the subject of the sentence e.g. Das is ein Apfel (that is an apple). You use einen in the accusative case which is when the verb is the direct object in the sentence. An example of this could be Ich habe einen Bruder (I have a brother).

I think its Akkusativ

That can you listen in the description under the lessons

Sie is a bit of an odd case. Here, sie is at the beginning of the sentence which means that there has to be a capital at the beginning. There's also Sie which is different, but you can tell that it is sie in this case because of the verb conjugation.

Capital "Sie" is they, "sie" is she.

Sie is also you, but "sie" is she/they and "Sie" is you. Since it is at the beginning of a sentence you can't look for the capital "S" to determine who it is, you have to look at the verb ending.

• Sie isst = she eats
• Sie essen = you (formal, singular or plural) eat, they eat (you need context to figure out which)

Hope that helps.

By looking at whether the verb ends in "-en" (plural Sie) or the feminine case

For it to be they, the verb has to be "Essen"

Exactly.

You use einen for a direct object

From the verb. Plural "Sie" verbs end in -en