After an apparent attack on their home-world (Cosine N to the 8th) from Earth that resulted in their planet's gravity beginning to increase, the planet's council send a female agent called Celeste to find out what happened and if the transmission could be reversed before their homeworld is destroyed. In order to aid her, her commander - a creature known only as 'Bag' - was sent with her to provide her with assistance wherever necessary. Due to her obviously alien appearance, Bag would hide inside a designer purse that Celeste carries with her.
Personality-wise, Bag shows no regard for humanity and is frequently pushing her belief on Celeste that Steve and his daughter Jessie are lying and hiding something in regards to the transmission that was sent to their home world. Needless to say, she is dedicated to aiding Celeste in their mission - even though this meant helping get Steve his job back so he could continue his research. Although she is Celeste's commander, she sometimes gives in to Celeste's demands - such as wanting to see the council when Steve asked her to marry him. On another ocassion when Celeste ordered Bag to release Jessie and give the dog its bark back, Bag complied - although not before telling Celeste that her attitude sucked.
Bag had many different abilities to utilise in order to aid Celeste. These included the following:
- Been able to create various objects almost instantly - including dresses, ID cards, Diamonds, etc.
- Providing information on various subjects - both through written description and video.
- Can change her voice to mimic others convincingly - which she uses during telephone conversations.
- Capable of telekinesis - allowing her to shut/lock doors and windows and levitate both objects and living creatures.
- Capable of boosting Celeste's own powers or providing her with others - such as altering another living creature's body density.
- Can control some power sources.
- A more random ability that Bag had was been able to silence a dog that was barking (so no sound came out its mouth even though it was barking).
When Steve finally realised how he had done the transmission (which was accidental), Celeste relayed this to Bag. However, she learns to her horror about the council's secret instructions for Bag to destroy Earth - 8 minutes after the signal is repeated. Despite Celeste's orders to leave Earth as they found it, Bag refuses - showing an image of Earth exploding when the countdown ends. Leaving Bag at home to try and avoid this after Bag refuses to stop, Celeste goes with Steve and Jessie to the facility. However, Bag rings Steve's brother Ron - pretending to be Celeste - and tells him to meet her at the facility after collecting her purse on the basis that her relationship with Steve isn't working out.
Ron later arrives at the facility with Bag - just as Steve, Jessie and Celeste are about to repeat the signal with the aid of his colleague and boss. Bag (still concealed) warns Celeste that she has 'signed her own death warrant', but Celeste ignores her and continues to help Steve and Jessie. Working together, the group are able to repeat the signal successfully - saving Celeste's homeworld.
When Ron tries to continue his conversation with Steve (under the presumption that Celeste rang him earlier), Celeste orders him to get rid of the bag as it will destroy Earth. However, Bag openly reveals herself and cuts the power to the lights - beginning the countdown to the destruction of Earth. Grabbing the bag from Ron (and despite Bag's almost insanely claiming that she is indestructible), Steve throws the bag into the Klystron, which was still under power from the lightning. Mutating into a giant eyeball, Bag proceeded to explode - with Earth saved from destruction.
My Stepmother is an Alien (Movie)