This is how The Sirencons and Starscream's plan goes in The Rise of Excelerator.
[At the Harbinger, the Sirencons bring Arcee to Starscream]
Harmo: We got her, Lord Starscream, just as you asked.
Starscream: Great job, Sirencons. Now put her in her dungeon!
Demo: So... What are we gonna do now, Lord Starscream?
Starscream: We... wait for them.
Demo: What?! You expect us to just sit here and do nothing?!
Starscream: [chuckles] Don't you see, dear Demo? The plan is that we captured Arcee, turn her into our servant and use her against the Autobots.
Demo: So, we're gonna use a song and turn Arcee evil while we're waiting?