Lanie Parish:  Kate , I talked Castle 's doctor into letting me look him over , and I came across a few ... strange things .
Kate Beckett: Strange how ?
Lanie Parish: No trace evidence on Castle 's clothes . But did find a key sewn into the lining of his pants .
Kate Beckett: What kind of a key ?
Lanie Parish: I 'm not sure , but it has " _ 38 _ " stamped on it . That mean anything to you ?
Kate Beckett: No .
Lanie Parish: Okay . Then there 's his blood work . I found antibodies to Dengue fever . That means Castle was exposed to the virus within the last two months .
Kate Beckett: Wait . Is n't Dengue fever tropical ?
Lanie Parish: Yeah ! It 's mostly found in Latin America , Africa , and Asia .
Kate Beckett: That does n't make any sense .
Lanie Parish: Neither does the bullet wound I found . Castle was grazed across the ribs .
Kate Beckett: Okay , that makes a little bit more sense . There were bullet holes on the boat .
Lanie Parish: But this wound was mainly healed . He was shot a few weeks ago .
Kate Beckett: A few weeks ago ? Are you sure ?
Lanie Parish: Maybe even longer . Kate , what the hell was Castle mixed up in ?