From the introduction:
The currents of space brought you to the tiny blue planet called Earth. You arrived as a microscopic organism: a spore evolved to withstand cosmic radiation and the million-year journey through the cold galaxy.
Now that you have arrived, you will be driven by a single need: to replicate and replace the most intelligent life form on the planet. You will grow into a pod, and after a short gestation period, you will emerge as a perfect replica of someone in your close proximity. Once you take their place, you will disperse more spores, and without being detected by the humans around you, you’ll attempt to overtake their society… One Replica at a time.
But there is one thing unique to humankind that your long evolution on distant planets hasn’t prepared you for: the complexity of their emotions. You will have to learn the nuances of their emotional language in order to infiltrate their world. The millions of unspoken ways people express themselves. The looks they give. The tone of their voice. Their body language… If anything, not being able to interpret these signals will be your Achilles’ heel.