Bilingual language behaviour is driven by numerous factors that are usually studied in isolation, even though individual factors never operate alone. Bringing together key insights from psycholinguistics and sociolinguistics, Luna Filipović presents a new model of bilingual language processing that captures bilingualism within and across minds. The model enables readers to explain traditional puzzles in the field, and accounts for some apparently contradictory reports in different studies. It shows how theory can be applied in practice and how practice feeds back into theory, with mutual benefits. Bilinguals are studied in action, when they interact with other bilinguals or monolinguals, when they recall witnessed events in real life and in the lab and when they translate and interpret for the benefit of monolinguals. This interdisciplinary take on bilingualism in action will lead to new research on bilingualism itself, and to applications in forensic linguistics and translation studies.