They assume the identities of Alan and Ann Granger (though they are not truly brother and sister) and enroll in Serena's school as transfers from France (though they don't know a word of French).
To survive, they must gather energy. To collect energy, they enlist the help of the Cardians, mystical monsters that are represented by cards. They can be summoned by the music of an eerie flute Alan always carries with him. They are sent off to gather energy.
The energy they collect isn't just for themselves. They must also feed their Doom Tree, a giant tree they have brought with them. Their lives depend on its survival.
But, just like with the Negaverse, Alan and Ann face the threat of the Sailor Scouts, and they soon encounter a new problem within themselves, something they don't know how to handle.
In their short lives, the two have never encountered or felt love, and when they feel it for the first time, they can't understand it too well. Alan develops a crush on Serena while Ann falls for Darien. Eventually, this problem escalates to the point that each wants to destroy the other's crush. Just when things couldn't get any worse, the Doom Tree goes wild.
Fortunately, it all ends happily. Alan and Ann discover love and, realizing their love, leave to start a new life.
The Doom Tree wasn't originally known as The Doom Tree.
Long ago, it stood alone on an island on a distant planet, surrounded by nothing but ocean, but then it decided to create Alan and Ann's race. It was then known as the Tree of Life, and they lived peacefully . . . until evil reared its ugly head.
The people of Alan and Ann's race started fighting each other, vying for control over the tree's energy. The Doom Tree tried to stop it, but the evil was too great, and their home planet was destroyed. The Doom Tree escaped with its few loyal followers and sought out a new home.
By the time the tree reached Earth, Alan and Ann were the only ones still alive, and the Doom Tree was too weak to help. Not knowing what else to do, Alan and Ann stole energy to keep the Doom Tree alive. However, the Doom Tree can only grow through positive energy, such as love.
Realizing that it had no choice, one day the Doom Tree takes the initiative and tries to solve the problem itself. In the process, however, it goes wild. Fortunately, Sailor Moon's cry to stop snaps the tree back to reality, and it regains its sanity long enough to tell Alan its story and to ask Sailor Moon for a favor: to cleanse it of the dark energy that has pervaded it. Sailor Moon fulfills that favor and destroys most of the Doom Tree, but a seedling remains, pure and new. With this second chance, Alan and Ann leave with the seedling in search of a new home.
