This passage occurs in the RCL Epiphany Season, Year B, most recently January of 2015.
Summary: The Greek highlights Mark's excellent dramatic skills. He uses tight language and subtle details to present the conflict of Jesus against the mysterious and powerful forces of evil. Evil is quite powerful here: It has invaded the synagogue; it knows more than the crowd; it is vulgar and disobedient to Jesus; its number if unknown. Yet Jesus will vanquish it and affirm the claim of the crowd, that he is one with authority. As Staupitz declared to Luther in the movie: "You are too hard on yourself; the devil has been around for thousands of years. Cling to Christ and his mercy."
How Mark employs Greek to add drama to the story:
1:21 and 1:22 All of the verbs in this sentence have verbs in the present or imperfect, suggesting a lot
of movement and continuous action. The story continues the whirlwind pace of Mark 1.
1:23 Mark puts the word "unclean" last in this clause, so it reads "there was in the synagogue a man in spirit unclean." A bit of suspense because as a reader it would not be entirely surprising to find a spirit in a synagogue. It is worth noting that the unclean spirit is not found outside the house of God, but inside the house of God!
1:23 The first aorist verb is ανεκραξεν ("cry out") suggesting an abrupt change in the action after all the other present/imperfect verbs.
1.24 The phrase here in Greek that the unclean spirit uses is "What to you and to me." This is essentially what Jesus to his mother at Cana: "What to me and to you." In other words, this is not a very kind way to talk! A sort of "What the hell do you want?"
1.24 The spirit switches back and forth between the singular and the plural, presenting an uncomfortable ambiguity: How many are there?
1.26 Interesting that even though the unclean Spirit obeys Jesus, it still gives off a μεγαλη (large) scream. This is the first use of mega in Mark. Furthermore, Jesus had commanded the spirit to be silenced; this shows its disobedience!
All of this drama and even highlighting of evil's power is designed to affirm the original claim of the people, namely, that Jesus is one with εξουσια (1:22), that is power!
Also, a side note, 1:23/26 the word for unclean is "ακαθαρτος" as in the man needs a cathartic experience...