Fugitive slaves also known as Runaway slaves were the slaves who left their masters and travelled without authorization. These slaves wanted to reach the territories that were free of slavery. After the 1850 Missouri Compromise, slavery was banned in Northern States and slaves from Southern states tried to get to northern sates. This new law forcibly compelled citizens to assist in the capture of runaway slaves.
When you infer you are making an educated guess about something or a topic your reading. When it comes to reading you want to make a logical guess about what you think the story is about