Daisy and Sweets are knocking boots when Bones and Booth walk in.
The two care about each other, even love each other, even if Sweets insists they're not right for each other. Unlike Bones and Booth, this facade blows away as Sweets and Daisy get together.
Cam in particular is moved by their work on bones of slaves from a slave ship, including those of Cam's ancestor. Putting the bones back together, and Angela's sketching of their faces, at last restores their identities as human beings.
The murder case comes when a person killed within the last month is found amongst the remains of the slave ship. Booth and Brennan are able to piece that together with the help of Hodgins (no thanks to his pink worms, however).