<Tr> <Th> No . overall </Th> <Th> No. in season </Th> <Th> Title </Th> <Th> Directed by </Th> <Th> Written by </Th> <Th> Original air date </Th> <Th> Prod . code </Th> <Th> US viewers (millions) </Th> </Tr> <Tr> <Th> 156 </Th> <Td> </Td> <Td> "Cutting Losses" </Td> <Td> David M. Barrett </Td> <Td> Siobhan Byrne O'Connor </Td> <Td> September 29, 2017 (2017 - 09 - 29) </Td> <Td> 801 </Td> <Td> 10.04 </Td> </Tr> <Tr> <Td_colspan="8"> Erin pleads with Danny, who has been contemplating retirement since Linda's death in a rescue helicopter crash, to help her with a case involving her ex-husband, Jack (Peter Hermann) who's been attacked in his office . Jamie and Eddie go undercover as a couple to bust a shady drug dealer; new mayor Margaret Dutton (Lorraine Bracco) butts heads with Frank . </Td> </Tr> <Tr> <Th> 157 </Th> <Td> </Td> <Td> "Ghosts of the Past" </Td> <Td> John Behring </Td> <Td> Kevin Riley </Td> <Td> October 6, 2017 (2017 - 10 - 06) </Td> <Td> 803 </Td> <Td> 9.49 </Td> </Tr>

Who plays the current mayor on blue bloods