This article deals with the interlanguage of adult second language (L2) learners acquiring finiteness. Due to the inaccessibility of bound inflectional morphology, learners use free morphology to mark a syntactic relationship as well as person and number features separately from the thematic verb, expressed by a pattern like "the man is go". Results from longitudinally collected production data of Turkish learners of Dutch are reported and present evidence for the claim that (a) verb movement and production of inflectional morphology develop separately in various developmental steps and (b) finite forms in nonfinite contexts (and vice versa) are by-products of this development. Moreover, all "is"-patterns in different Germanic languages can be explained by the application of minimalist theory of verb movement and recent views on morphology. "Is"-patterns that correspond neither to the first language nor to the L2--a poverty-of-the-stimulus problem--turn out to be possible in other languages of the world and are constrained by Universal Grammar.