Green’s Dictionary of Slang

1. to allow someone to join a scheme or conspiracy.

1897		Daily Tel. 12 Feb. in Ware (1909) 211/2: It’s very likely the sellers and the general public concerned in auction sales are anything but satisfied with the results of sales by auction where a ‘knock-out’ is arranged, and especially where the auctioneer ‘rows in’ with the crew.
1909		J. Ware Passing Eng. of the Victorian Era.
1930		(con. 1910s) D. Mackenzie Hell’s Kitchen 84: Often a new-comer who was a friend of Millie’s would be asked to ‘row in’ (participate in the deal).
1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 9: Row in: To take part in deal.
1956		J. Curtis Look Long Upon a Monkey 37: That’s another of the reasons for wanting to row you in on this.
1970		Galton & Simpson ‘Cuckoo in the Nest’ Steptoe and Son [TV script] harold: So it’s official now, is it? He’s rowed himself in. albert: He has agreed to join the firm, yes.
1979		F. Norman Too Many Crooks Spoil the Caper 58: I told ’im it was OK to row Tony in on it, providin’ the Williams bruvvers didn’t stick their oar in.
1989		T. Blacker Fixx 54: I used to row him in on many of my better schemes.

2. to implicate a suspect in a crime.

1930		(con. 1910s) D. Mackenzie Hell’s Kitchen 89: These informers are for the most part ‘rowing in with’ (working with) both sides. [...] These are the men whom you know as ‘stool pigeons.’.
1970		‘Metropolitan Police Sl.’ in P. Laurie Scotland Yard (1972) 327: row in, or out, to: to make an action implicating or exonerating a person from a crime in the eyes of a third party.

3. to include.

1910		‘Doss Chiderdoss’ ‘Unseemly Hilarity’ Sporting Times 22 Oct. 1/3: To row in with the fashion, she acquired a ‘hobble’ skirt.
1965		G. Melly Owning Up (1974) 68: He [...] thought it was very mean of me, a fellow singer, not to row him in.
1979		F. Norman Too Many Crooks Spoil the Caper 15: He eyed me sternly. ‘Did Louie row yuh on the firm, or wot?’ ‘I wasn’t in on anything,’ I said.
1984		‘Derek Raymond’ He Died with His Eyes Open 112: Suppose I match that, find Babsie, row in my old boiler and make it a four? How’s that grab you?