Some science-fiction stories have been deployed so frequently that it seems as if they might be utterly exhausted. The ‘first contact’ narrative is one such: aliens arrive on Earth and are either malevolent (go, humanity!) or peaceful, whereupon we silly primates act aggressively towards them (oh, humanity!). It is therefore especially commendable when a writer is able to take such a tried and tested narrative and find something new, enlightening and bold in it. Nnedi Okorafor’s Lagoon manages just that, and disrupts the standard alien arrival clichés in numerous ways.